Bake, Boil & Brew

  Some beautifully simple and primitive forms of baking can be accomplished over just an open fire. Delicious soups and stews can be created from almost nothing.   Soups and stews were historically more commonplace in yesteryear’s kitchens than they are today, but for good reason.   With sugar becoming more affordable in the 16th century, exciting new beverages called “small beers” would appear.   These carbon dioxide holding, sweet and fizzy fermented beverages would evolve into our modern day “soda pops” which are now consumed daily by the billions, worldwide.   These primitive breads, simple soups and old style effervescent drinks are easy to make.

Ash Cakes

 _ One can bake a primitive but tasty bread in a fire without using pot or pan.  A soldier in the Continental Army 200 years ago or a legionary in the Roman army 2,000 years ago might have been given only raw flour as part of their daily ration and both were expected to know how to cook it.  Mixing flour with water and cooking it as a wet gruel was one option.  If on the march and having little or no time or utensils to bake a more proper bread, then turning flour into ash cakes was usually more favorable than eating gruel.  One simply added a small amount water to the flour and mixed it up.  The mixture was then rolled around in the hands and kneaded a little before being dropped onto a flat hot rock, a piece of tree bark or simply dropped into hot but not flaming ashes at the side of the fire.  The cook tended it carefully, tilting it or flipping it as necessary.  The ashes which are thoroughly sterile don’t really cling to the bread later and can be blown off easily.  Another way that the Romans occasionally cooked the same flour ration, was to roll the dough into a little rope and then swirl that around a stick.  The stick was stuck into the ground and leaned over the fire like a diagonal spit.

About 75% of a Roman legionaries diet was issued as a ration of grain and it was up to them to cook it.  Had they the time, legionaries usually prepared their breads in advance of a march.  For short term consumption (say within 4 or 5 days) they might have baked leavened breads or unleavened type breads akin to pita (Gk).  For a longer lasting bread resistant to spoilage they might have over-baked something similar to what we now recognize as a “hardtack” or “sea biscuit”. 

A contuberniam (the smallest organized unit of soldiers in the Roman Army / about 8 men) slept in the same leather tent (usually of goatskin & waterproof), traveled with their own portable stone gristmill (a quern or quern-stone) and baked in a small portable 2-piece ceramic oven called a clibanus.  When a Roman army marched or moved to a new location they carried a lot of food and equipment with them.  Each legionnaire was loaded down with personal gear while non-combatant servants led pack animals or wagons loaded with the contuberniam’s heavier items in a supply train which followed the legion.

*  When on the march Roman legionaries carried a small personal utensil known as a “patera” to drink and eat from.  A patera along with a spoon probably composed the first military issued mess kit.  A larger bronze pot or kettle was probably shared by the whole contuberniam.

 

*  Corn or maize was a New World plant and the rest of the world was not introduced to the crop until the 16^th century.  Corn is generally identified as being either flint or dent type.  Flint corn has kernel tops that are round, and dent corn kernels are marked with a dent or dimple.  Popcorn and sweet corn are flints while yellow corn hybrids grown for cattle feed or ethanol production are examples of dent corn.  Hominy is”nixtamalized” by soaking it in an alkali solution like slaked lime or lye.  This process reduces the presence of mycotoxins and releases more proteins and niacin for digestion.  Corn has no gluten and so without the help of another flour that contains gluten, it will not bind together or rise like a normal bread.  Hoe cakes, corn dodgers, corn pone, johnny cakes and hush puppies may have occasionally been made with only cornmeal in the past but most modern recipes call for a little wheat flour to be added.

* “Parched corn”: When corn kernels mature they get very hard; so hard they become almost impossible to eat.  So hard that it is very inconvenient to crack with a mortar & pestle.  The Native American “Indians” that cultivated corn also devised the stone “metate” to crush the suborn kernels. Soldiers or travelers carrying these stubborn seeds learned that they could roast them in a pan over the fire. A few of the kernels might pop.  This process called “parching” the corn tenderized it, simplifying the task of grinding and then cooking the kernels.

*  It is possible to boil a small amount of water over a fire without any special utensil.  Water can be placed over a fire in broad leaves or in a broad strip of tree bark.  Because of the absorption of water, the fire is prevented from burning through.

_ “Hardtack”, “sea bread” or “sea biscuit” is an old, primitive form of bread that was valued for its robustness and resistance to spoilage.  Before a voyage, a ship was provisioned with many barrels full of sea biscuits.  A water tight cooperage was not required because the commodity contained within them was not liquid.  Therefore weevils might eventually find their way into some of these cheaper kegs (cask or “barricas” in Portuguese & Spanish).

_ The regulation sea biscuit was well standardized by the British Navy before the 17th century.  It took about 4 sea biscuits to make a pound; part of a sailors standard daily ration was 1 pound of bread.  But it was a salty, wood hard, unpleasant bread that usually required a soaking in something before it could be eaten.  Whereas normal baked breads would quickly mold and plain flour would go rancid or become bug infested on a long sea trip; the salty, hard, twice or triple baked sea biscuit if stored properly, could last several years before being consumed.  Sea cooks when in need of a flour could still crush up sea biscuits with a hammer.  “Hardtack” became a popularized term for the same bread about the time of the American Civil War.  A traveler, explorer, soldier or pioneer could tie a bag of these to his pack-horse and not worry about them crumbling apart after months worth of physical abuse.

The recipe for hardtack or sea biscuits is super simple, the detail is in the baking.  Whole wheat flour, salt and a little water are the only ingredients.  Only enough water to make a stiff dough is necessary.  The dough is kneaded a little bit, then separated into balls which are squashed flat to the size of a crumpet or big cookie.  It’s usually perforated a little on the top to let gas escape while it cooks.  There is no set salt ratio in most recipes but the amount usually seems excessive.  Salt has been mankind’s first and most effective chemical food preservative. The baking needs to be done slowly, dehydration is the main goal.  In the archaic ovens of yesteryear this might have taken all day.  Between Latin and Old French languages the word “biscuit” itself means – “twice cooked”.  Usually two days then in an earth oven to get that hardtack dry.

*  Earth ovens, pizza ovens and hornos work by absorbing and trapping heat.  A hot fire is built within them and is allowed to burn down before the embers and ashes are swept out.  The goods to be baked are inserted and the opening is then closed off to seal in the heat.

* A thoroughly effective oven can be made on the ground with the help of a large clay or metal pot. A fire is built over a flat rock or hearth of bricks to heat them up. The coals and ashes are then brushed away, the dough placed on the hearth and then the pot is placed over the dough. Wet leaves, twigs and straw can be placed over the pot and then the hot coals placed over that. The intent is to maintain a slow, smoldering heat around and above the pot and not to let it burn hotly.

Fluffier breads

_   Now is not the time to get bogged down with long explanations of quick-breads, leavening and sourdough.  These topics are briefly discussed in an older post (Yeast & Fermentation) anyway.   Quick-breads are relatively new and rely upon a chemical reaction from ingredients (soda and acid) that are mixed into the flour.   When moisture is added then gas bubbles are formed and expand the dough, making it “rise” artificially.   Sourdough is ancient; it is a bread made from leavening (yeast culture) which might have been passed down from mother to daughter throughout the ages.   Before yeasts were identified under a microscope, people did not know what device in leaven caused breads rise.  Now we know that enzymes convert starches to sugars and that yeast digest sugars to create ethanol and carbon dioxide gas.   When wet, the sticky gluten in flour traps the gas from fermentation, allowing the dough to inflate.   Sourdough then implies a bread made from a wild yeast culture and perhaps some beneficial lactobacillus bacteria as well, but also the word sourdough implies a practice wherein a portion of each new sponge (dough) is withdrawn and saved to be used as the “starter” leaven for future use.  Pioneers, expeditions and army chuck-wagon cooks brought their sourdough starter (leavening) with them; because doing so was easier and much faster than attempting to create a new yeast culture from scratch.  Over time the more durable cast iron Dutch oven would eventually replace the ceramic clibanus as the ideal utensil to bake with over an open fire

Soups

_  Whenever there was a fire in the average home of yesteryear, pots or kettles of hot water and soup were constantly maintained close by the fireplaces or stoves.  The soup pot was in a constant state of cooking and was seldom ever completely emptied.  Any vegetables, grains or small scraps of meat and more water would be tossed into the pot whenever the occasion arose.   In the cold of winter this practice was thermodynamic-ally accommodating because the liquid in the pots collected or banked thermal energy and slowly released it back into the house if or when the fire died down.  Importantly though, cooking in a pot conserves the oils, fats and nutrients from food that would otherwise drip off into the flames when grilling for example.

_  Copper and earthenware pots and cookware have been used at the hearth for eons.  By the 17^th century however the state of the art and the most desirable cookware to be found in Europe was cast from brass.  The Dutch reputedly produced the best cast cookware.  At the onset of the 18^th century an Englishman visited a foundry in the Netherlands, learned their sand casting technique and then began to duplicate the casting of brass cookware back in England.  Copper, bronze and brass are expensive metals though so he began to experiment with cheaper cast iron.  After much trial and error he eventually became successful in casting iron cookware from sand molds and patented the process in 1707.  The next two centuries saw a boom in the worldwide demand for this cast iron cookware; especially for the robust lidded pots meant to sit right down in the fire, called “Dutch ovens” (by everyone but the Dutch).

* China, India, Japan and Korea had a long history of cooking in iron vessels but these were not produced in large numbers.

* Cast iron cookware was tough and versatile and became almost indispensable to the daily life of a household. When conditioned and maintained correctly cast iron skillets have better and more durable “non-stick” surfaces than the newest pans with Teflon or ceramic coatings. Large cast iron kettles or cauldrons were used over fires outside to boil water for laundry, to scald chickens or pigs and to render tallow for making soap. Cooks might have used a single Dutch oven to boil, bake, fry, stew, or roast. When writing a will, mothers sometimes divided their beloved cast iron cookery up between favorite children. During the 1804-1806 Lewis & Clark journey across the continent it is noteworthy that the 31 man expedition carried not one but two heavy Dutch ovens on the trip. One of the ovens fell out of a packsaddle, rolled down a hill and shattered though. Still the metal fragments made useful gifts and implements of barter to Indian tribes met along the way.

 

_  Nutritious  soup can be made from most anything, like leftovers, table scraps of skin and bone or unused vegetable parts.   Starving people have even been known to boil their leather belts & shoes, which is not as crazy as it seems.  The major component of leather is a fibrous protein called collagen.  Gelatin which is a foodstuff made by the tons commercially, is made from the collagen in ligaments, bones and raw (untanned) animal skins.  Gelatin finds its way into many processed foods, including ice creams, marshmallows and candies. 

  A talented cook often begins a soup with an available stock or broth, which might have already been made and on hand from a few days before.  A stock or broth might serve a cook in many ways besides being used as just a soup base though.   In a busy kitchen, stock is commonly started whenever there are some useful bones or meat scraps laying around the kitchen, that might otherwise go to waste.  Any lidded pot will do or an electric “crock pot” too,  but the best stockpots for the modern stove top are big, thin and made of stainless steel.  The most useful size ranges between 1 and 3 gallons in volume (4-12 liters).

Making a stock

_  Perhaps a day or two after a holiday dinner there is a goose, chicken or turkey carcass in your refrigerator.  The prime sections of meat might have been sliced off or pulled away but what is left is skin and bones and small, less desirable pieces of meat.  A good cook would gather up all that scrap up and toss it in a stock pot, add water to submerge the carcass and then set the stove to a low heat, simmering it for several hours or for the rest of the day.  That experienced cook would also undoubtedly add some onion, carrots and celery, and perhaps add some bay leaves, parsley and thyme.

_  Stock is usually not boiled because that creates a murky liquid.  Fresh meat or bone scraps create just as good or better stock than previously cooked ones will, however smoke and barbecue flavors from cooked meat carry over especially well.  Other vegetables or vegetable peelings and spices can be used.  A toss of wine can compliment the final taste.  After it has simmered for a long time most of the flavors and nutrients will have been drawn into the liquid.  The stock is then poured or strained into another container and the solids are discarded.  After being chilled, a layer of gelatin will usually form at the top of the stock or completely through the stock in a well executed example.  In a refrigerator the broth might enjoy a grace period of several idle days before it really needs to be used.

_  Pork or mutton stocks are rarely made because of the fatty oils and yellowish coloring they produce.  Poultry and beef seem to be the most popular stocks but ham and fish stocks are also encountered.

Examples of stock based soups:

-* Borscht is a Russian soup made from meat stock and beets.

-* Consommé is a very clear soup, deviating little from regular meat stock except that it has been clarified by using egg whites to remove fat and sediment.

-* French onion soup is made from stock and browned onions and was frequently used as a concession to the poor because of some obscure French law that required all restaurants to offer something appreciably affordable on their menus.

-* Bisque originally referred to a thick cream soup made from the broth of shellfish like crab, shrimp or lobster.  In an authentic bisque, the shells are ground to a fine paste and added to thicken the soup.  Today it is common to see cream-based soups that do not contain seafood.  Thanks to the modern blender or food processor we have added pureed mushroom, squash, tomato and red pepper to our “bisque” repertoire.

-* Vichyssoise sounds French but it might have been American in origin. It contains chicken stock, leeks, onions, potatoes and cream.

_ “Condiment soup” is not entirely a joke because it can have practical applications and be useful survival advice of a sort.  Winter life in an alpine ski village can be otherworldly.  Whether in American or in the finest European ski resorts, civilization is precariously perched upon slick, cold and inhospitable slopes of deep snow.  Skiing or snowboarding is foremost a sport for the affluent.  At the base lodges or midway lodges further up the mountain, cafes and small restaurants do exist but their prices for food and beverages are truly exorbitant.  There is a class of young but poor skiers who manage to play at these resorts because they preform menial work there.  They might drive snowplows, do room service, operate gondolas or chairlifts, bar-tend or preform ski patrol duty. These workers are lucky enough just to get lift tickets or to find places to sleep at night on their minimal pay.  They aren’t going to be able to afford a sandwich or hot drink at the ski lodge when prices are inflated five or six times what they should be.  When one of these working class skiers stumbles in from the cold; their hands and gloves cold and wet, their nose and cheeks beet red and shaking from hypothermia, then they can either purchase amenities at outrageous prices or turn to the ski bum’s condiment soup.

_ The whole plan depends upon disposable cups, refills of free hot water and a condiment bar.  Usually individual packets of seasonings like mayonnaise, tomato ketchup, mustard, pickle relish, coffee creamer, salt, pepper and sugar are to be found at the condiment bars.  Sometimes crackers, diced onions and tomatoes, shredded cheese and more exotic flavorings like tartar sauce, chili sauce or Chinese hot mustard can be found also.  The skillful ski bum then with cup of hot water in hand, takes note of the available condiments and crafts his hot cocktail accordingly.

 

Sugar and Carbon Dioxide

_ Coke® is but one flavor or one brand of soft-drink and yet for every day that goes by almost 1.2 billion servings of Coke alone are consumed around the world.  The average American drinks an estimated and unhealthy 44.9 gallons (170 L) of “sodas” per year. Aside from flavor and cool serving temperatures the primary elements making soft-drinks so addictive are sugar content and the carbon dioxide fizz. 

Soft-drinks are mildly acidic because when carbon dioxide gas is added, it dissolves into solution and forms carbonic acid.  The source of the dissolved carbon dioxide in a given soft drink might come from a brewery that sells the gas as a byproduct or could be captured and purified waste gas from factories or power plants that are required to trap the greenhouse gas.  Most colas (like Coke) have food grade phosphoric acid added as well to add “bite” to the taste.  Today in a manner similar to soft-drinks, almost all commercial beers too are deliberately injected with pressurized CO2, before sealing the can, keg or bottle.

In earlier times though CO2 gas was created within a closed bottle by adding a little priming sugar or malt before capping it shut.  The results are less uniform when using this “secondary fermentation” procedure; beers can turn out flat if not enough gas is made or can burst the bottle if too much gas is made.  Champagne predominantly uses only the secondary fermentation method to create gas within the bottle.  Since bubbles are the hallmark of Champagne and other sparkling wines, more gas than usual is dissolved within these beverages, so bottles must be made extra strong to withstand the extra pressure.

_  Kombucha culture, kefir grains and ginger beer plant are examples of SCOBY s (Symbiotic Cultures of Bacteria and Yeast).  These are gelatinous or semi solid cultures of a mixture of microorganisms.  Much like sourdough starter, a portion is separated and used to begin a new fermented drink but the starting culture is maintained independently.  Drinks made from cultures like these are often associated with the newly coined term “probiotics”.   Supposedly these live probiotic microorganism improve gut flora, help the immune system and provide other health benefits.  Many uniquely flavored drinks can be created from using cultures like these, and all are fermented, slightly alcoholic and lightly effervescent. 

The Kombucha beverage is a fermented sweet tea probably originating from Russia or China, and prepared by many today for its supposed health benefits.  Milk kefir originated in the Russian/Caucasus/Turkish area and might have a sour taste similar to thin yogurt.  Beet kvass is a traditional Russian beverage started from a milk or water kefir culture, where beets and scraps of wheat or rye bread and a dash of salt are thrown together to ferment.  There are apple, berry and raisin versions of kvass too.

“Ginger beer plant” is an older (1700s British) name for a symbiotic culture that might have been used to create a batch of “ginger ale” or a host of other flavored-fermented beverages depending upon the herbs, leaves, barks or roots used.  “Small beers” that created such a taste sensation four centuries ago may or may not have depended upon these gelatinous cultures for a start.  There are plenty of yeasts and beneficial bacteria on the herbs and roots used or floating around in the atmosphere.  What really permitted the small beer and resulting soda-pop phenomenon to occur in the first place– was the introduction of sugar as a plentiful food source.

* Sugarcane is just a huge tropical grass that originally grew in humid Southeast Asia.  For the longest time refined sugar was considered a rare and expensive spice by Europeans.  Sugarcane wouldn’t grow as a crop in Europe because of the harsh climate.  On his second voyage Christopher Columbus brought the first sugarcane roots to the Caribbean to test the plant for cultivation.  Soon sugarcane plantations would sprout up on several islands.  With too many islands in the Caribbean for Spain to control, French, Dutch and British traders and privateers would establish separate communities there too a bit later.  By the 1620’s processed sugar and molasses from sugarcane would become a significant cash crop for these latecomers as well.

* Sugar from sugar beets was never realized until a German chemist noticed that the beet roots contained sucrose. The first refined beet sugar commodity appeared around 1802.

* HFCS (High Fructose Corn Syrup) is an unnatural, biochemically different sweeter that must be processed differently by the body.

Small Beers

_ Back say two or three centuries ago everyone in the family with visitors and servants included would drink the household small beer if it was available and it usually was.   Children drank it for breakfast like they would cold orange juice or refrigerated milk today.  The alcohol content was usually minuscule, probably seldom reaching 2.5 ABV.   At its heart a small beer was a weak infusion of some root, bark, spice or fruit boiled in water, to which sugar and yeast were added and allowed to ferment for a few days.

Today we think of ginger ale and root beer as being flavored soft drinks but they actually started out as small beers.   Today the term “ginger beer” is used to differentiate the alcoholic version from the soft drink version “ginger ale”.  Either a batch of ginger ale, ginger beer or root beer can be begun with the help of a “ginger beer plant” SCOBY mentioned earlier.  But these beverages can also be started with something simpler called a “ginger bug” instead.  A ginger bug is similar to the more dedicated ginger beer plant SCOBY, but is a younger, liquid / not semi-solid colony of microorganisms.  To create a ginger bug one simply slices some fresh unpeeled ginger root into a jar of sugar water and leaves it exposed to the air on the kitchen counter top.   Every day a little more ginger and sugar might be added.  In a week or so wild yeast and bacteria will be caught and bubbles of carbon dioxide will be seen rising in the jar.  Ready to use now, a portion might be saved away as a sourdough starter would be while the other portion is used: added to a sweetened tea like infusion or a sweetened decoction of boiled roots or something.   If ginger ale is the target beverage then the ginger bug itself would probably provide insufficient ginger flavor.  In this case one usually creates a separate strong, sweet ginger tea and then adds the ginger bug starter to that.

_  Long before the Pilgrims landed on Plymouth Rock the local Indians were boiling up sassafras roots which are sweet, to make a kind of tea.  Along with the growing accessibility of sugar, it did not take long before European colonists joined “old world” knowledge of brewing techniques, with new indigenous flavors to create “root beer”.   Many different root beer recipes existed and employed an assortment of ingredients.  The central or most common ingredient in most variants of root beer was the sweet root of the sassafras tree.  Depending upon recipe some other typical flavorings in root beer were sarsaparilla, ginger, licorice, birch, juniper, hops, wintergreen leaf and dandelion root.  Almost none of the flavors in today’s commercial soft drinks are natural any more, but are instead artificial flavors and frequently synthesized from petrochemicals

* In the 1960s the FDA outlawed the use of sassafras in commercially made root beer.   It seems that some laboratory study identified the key polyphenol in sassafras called safrole and determined that it could cause cancer in lab rats if they were fed massive quantities for a long time.   Sassafras root probably contains no more safrole than basil, nutmeg or cinnamon but these items obviously were not taken off the market.

* Sarsaparilla comes from a tropical greenbrier type climbing vine.   It is not native N. America but is to Central and South America, and the Caribbean Islands.   The local Carib Indians were drinking sarsaparilla health tonic type tea before the Spanish got there.   Extract from the vine has been valued for centuries as medicine for treating illness like eczema, contact dermatitis, psoriasis, syphilis and arthritis.  It is easy to imagine that this new medicinal commodity shared the same boat ride along with sugar, to all points of the compass.    More sarasaparilla history:

* Birch beer originated in the 18th century as small beer flavored with the boiled extract of bark, twigs, sap and roots of the black birch tree.

* Europeans found Native Americans around Quebec drinking a spruce tea of a type, early in the 16^th century.  Later in the 1700s several enlightened people were concocting “Spruce Beers”.  The tender buds at the tips of branches or sprouting new trees were sour, complimented the taste of sugar water and were eventually determined to prevent scurvy (because of the “vitamin C” content).  Both Benjamin Franklin and the intrepid Captain James Cook recorded recipes for making spruce beer but the volumes they used or proposed were very large.  Cook’s Spruce beer  / Univ of Wellington

* Beer on Board in the Age of Sail / someone else s blog post

Carbonation

_ Not all soft drinks sprouted from the sugar fermentation / small beer route though.  Sparkling mineral water from a spring must have been mankind’s first encounter with carbonated water.  If that water is still considered safe and is bottled for sale, then it might contain minerals like potassium, sodium or magnesium.  By the tail end of the 1700s chemist were toying with the notion of making artificial sparkling water.  Someone discovered that they could place dissolved carbon dioxide into water by dripping sulfuric acid onto chalk and then bubbling that gas up through water.  In English this product might have just been called “seltzer water”.  Fruit juices and perhaps ice were mixed in for a taste sensation.  By 1819 a patent was issued for the first “soda fountain” which actually used a pump and spigot to dispense the carbonated water into a flavored syrup.  By the 1830s new methods of production allowed for the cheaper carbonation of seltzer water and soda fountains were springing up all over the place.  Aside from mineral water and seltzer water are a couple of other clear sparkling beverages known as Club Soda and Tonic Water.

_ Club Soda is predominately seltzer water, with sodium bicarbonate, sodium citrate, disodium phosphate and perhaps some sodium chloride thrown in. 

_ Tonic Water came about though because quite a while ago some British soldiers deplored the awful taste of their malaria medicine, so they added soda and sugar (and later gin) to the water that the bitter alkaloid powder was dissolved in.   (A Jesuit priest brought quinine back to Europe from the wilds of Bolivia and Peru about four centuries ago).   The medicine quinine is very bitter and comes from the bark of Cinchona or Quina trees.   The alkaloid interferes with the reproduction of malaria-causing protozoa and is still used to combat malaria today.   In the past quinine was in higher demand around the world and the Bolivians and Peruvians became greedy over export of the tree bark.   The Dutch smuggled seeds out of South America and began growing Quina trees in Java.   Just before WWII, plantations in Java were producing 97% of the world’s quinine.   The Axis takeover of the Netherlands, Indonesia and the Philippines during the war caused a severe quinine shortage for everyone else in the world that suffered from malaria.  Used mainly in the famous British “Gin and Tonic” cocktail, the soft drinks called “Tonic Water” today are much more docile tasting than they once were because they contain much less quinine hydrochloride.   Carbonated water has also replaced the sodium bicarbonate component.

 

 

 

 

 

Isometric Camouflage

“Camouflage” was not an existing word back in 1890 when the Darwinist-zoologists Sir Edward Poulton  wrote his book ‘The Colours of Animals’.  It was not yet a proper word even later in 1909 when Abbott Handerson Thayer  wrote his controversial book entitled ‘Concealing-Coloration in the Animal Kingdom’.   With a vocabulary more limited than now, Thayer’s work began by explaining how an otherwise, utterly conspicuous bird like the male peacock could veritably vanish inside a forest.

The Italian verb “camuffare” means to hide or disguise.  The French verb “camoufler” similarly means to conceal or cover up – as a theater actor might apply makeup right before a performance.  The French word “camouflet” is used as a noun perhaps to depict a snub or an insult or it might describe a crater in the ground caused by an underground explosive.  Camouflet might be the smoke blown into someone’s face as a practical joke.  The word “camouflage” is newer; possibly dreamed-up during the trench warfare of WWI, by some French infantryman as he lay freshly covered over with dirt excavated by nearby artillery bombardment.  In the last century the definition of this new word camouflage, has swelled to include many types of deception to the eye or subliminal trick to the brain.

  The concept of camouflage is very old.  Mother Nature itself is resplendent with convincing examples of camouflage.  Both below the water or above, most predators and prey alike participate in the masquerade of visual deception.  Even plants play the game.  Some plants deliberately attract while others can effectively repel pollinators or herbivores with their looks alone.  Thousands of years ago aboriginal hunters might have been the first humans to use camouflage, if they wore animal skins as a disguise to hunt game.  From time immemorial camouflage has proven to be a very advantageous survival tool for a great many living things.  It will continue to be so tomorrow.  Mankind today being no exception, has need to hide from himself.

Why does it work?

Not all “camo” is good camouflage.   Some military camo is really poor.  At best even the majority of nature’s camouflage schemes are specialized or static and so will succeed only for a limited set of circumstances.  Some fish, chameleons, squids and octopuses though are luckily equipped with the ability to dynamically change their disguises.   Chromatophores present in their skins empower this magical ability.

Color is certainly not the only important component of successful camouflage.  With humans in fact, color-blind individuals have been actively sought for as airborne artillery spotters or as snipers by the military, specifically because they are not distracted or fooled by colors.  These people with unusual red-green color receptors in their eyes may be better equipped to see certain underlying contrast that outline the shape of a threat.  Though color is still important to the average eye, any eye can still be led astray by other, more subtle mechanisms.  Mechanisms, some of which to be explained shortly.

Sophisticated modern optics and hypersensitive sensors are being exploited on the battlefields now.  Effective military camouflage schemes today and in the future will need to work for a broader electromagnetic spectrum, which means masquerading even in non-visible light.

Contemporary with the Napoleonic Wars, military uniforms were usually bright and colorful.  The British and Danish armies were fond of red coats, the Spanish, Austrian and Saxon armies favored bright white or light gray, the Poles, Prussians and Napoleonic French wore dark blue colors and the Russians wore green.  The arrival of more accurate firearms with longer reach due to the rifling of barrels, changed that.  By the time of WWI most progressive armies had switched to low visibility clothing and soldiers were now hiding behind objects for protection rather than standing starkly out in the open.

To be sure there were some isolated incidences of soldiers wearing camouflage well before WWI.  For example Rogers Rangers who participated in the French Indian Wars, wore uniforms that were dyed green.  The French led Wabanaki Confederacy natives that they opposed, wore deerskin if anything and were harder to see.  On the other side of the planet and around 1846 a British officer of an Indian Army regiment had his whole troop go down to the river and rub mud into their new white cotton uniforms.  Later still and on yet another continent the first “gillie suits” for snipers were used by Scottish soldiers fighting in the Boer Wars of South Africa, a decade before WWI.

camouflage netting

 

<Expandable Thumbnails follow>  the “tiger-stripe” camouflage worn during the Vietnam War provided good concealment in the jungle.  The French introduced the pattern.  The American uniform versions were great at first but due to faulty dyeing processes – would fade badly after a laundry wash.

The coat below would work as camouflage in a room full of steaks.

Below is an example of bad camouflage.  It’s a three color patten of shapes with a tiny scale.   The uniforms must look like homogeneous pea soup from a distance.

Any notion that one camouflage can be appropriate in many different environments is a preposterous proposition.  Nonetheless this silly one-for-all camo notion continues to be funded, researched and tested.  The reason is that an organization like the Army, or any other branch of military service, works as a team.  Basic military psychology dictates that members of a team should look and dress alike.  Each of the individual services wants a new, modern, high tech look.  Outfitting hundreds of thousands of soldiers with four or five sets of new uniforms and accouterments soon gets to be very expensive.  In 2004 the US Department of Defense spent $5 billion to outfit the Army with a new pattern of camouflage uniforms.  Then the Army decided they didn’t like it.

The computerized, digitized, scientifically analyzed UCP (Universal Camouflage Pattern) adopted by the US Army a few years ago is a prime example of a camouflage flop.  Some fundamental design considerations were ignored.  The omission of black was a stupid decision.  The pale, cement colored, pixelated UPC could only look natural for someone standing inside a rock quarry.  The Army might have been wiser to stick with solid, century old khaki, olive drab or feldgrau colors.

There is nothing wrong with pixelated patterns but don’t buy into the gimmick that computers can make camo planning decisions.  UPC was a three color camo scheme where the contrast was too insubstantial.  Additionally the scale of the contrasting regions was too small within UCP.  Most camouflaged uniforms though, mistakenly use too small a scale of pattern.  There is little need to deceive the enemy’s eye at close up range, but greater need to fool it at rifle or battlefield range (300 meters).  The chunks of contrasting colors need to be much larger to affect an observer from distance.

There is still great room for improvement in the world of military camouflage and it is a realm where the psychologist with discretionary artistic skills can still innovate.  No doubt there are as yet, still undiscovered and inventive ways to lead the eyes astray.

Principles

It is from nature that mankind gets his camouflage ideas.  In nature you find both plants and animals exploiting cryptic coloration to hide or mimicry to impersonate something else.  Some of the flowering plants (especially some orchids) practice a highly developed mimicry.   The intent is usually to attract bees, wasp or flies to assist in pollination.

< * Of the many borrowed photographs to follow: first, they have been declared to be of public domain; second, wherever possible an effort has been made to embed attribution and source metadata into each JPEG photo – should it be examined or downloaded. >

 

The snake below left is a Texas Coral Snake. It carries a dangerous neurotoxin, instead of a hemotoxin like pit vipers employ. The harmless Mexican Milk Snake on the right mimics the coral snake but belongs to a completely different Family and Genus of snakes.

 

As if the imitation of a stick isn’t good enough, the phasmid below also carries its tail higher than his head, offering a less crucial first target to a predator.

 

Anti-Camo

Completely opposite to camouflage, some organism use gaudy, stand out coloration to deliberately attract attention to themselves.   It is used as a signal which says – don’t touch me or bother me.   Since the majority of organism that use this scheme are toxic or venomous, would be predators avoid them or suffer the consequences.

 

 

Countershading

The phenomenon of countershading went unappreciated until about a century ago when the naturalist and artist named Abbott Thayer (who painted the peacock mentioned earlier) first identified this mechanism.  Thayer noticed that many animals have a dark upper body but a lighter underbelly.  He reasoned, that these animals when illuminated by sunlight from above have their overall appearance flatted or dulled rather than accentuated.

The illustration on the left is from Thayer’s original book, right side from Wikipedia.

   Disruptive coloration and alternating shapes in camouflage attempt to visually scramble the contour or outline of a subject.  A net thrown over an artillery piece interrupts or breaks up the outline of the cannon.  A disruptive eye mask or eyestripes on many an animal helps disguise its vulnerable, usually dark and distinctive eyes.  Shapes or patterns that are distractive enough will lead the eye away from the edges or outline of a form.  The coloration in these disruptive patterns are often strongly and abruptly contrasted.  Symmetry is carefully avoided, because animal brains are wired to notice spatial correspondence.

skirting

Notice the semi-circles created by contrasting light – against dark bands on this viper below.  Notice how the markings run perpendicular or counter-intuitive to the body’s axis.  These markings disrupt quick interpretation of the viper’s contour by offering a more attention getting alternative for the viewer’s eye.

eye stripe

Below, notice the direction of the disruptive stripes on the legs.

Cubism and Dazzle camouflage

A noteworthy art movement beginning at the dawn of the 20th century was known as “Cubism”.  With cubism the art does not necessarily try to make a 2-dimensional canvas look 3D, but it does attempt to depict a subject from multiple viewpoints.  In cubism the elements of a subject are broken up and are then reassembled in an abstract form.  (*The following examples of cubism are declared public domain by virtue of their old age – which here exceeds 75 years).

This slideshow requires JavaScript.

The stark designs put on ships beginning with WWI are known as “dazzle camouflage” and have roots or kindred elements with cubist art. The purpose of dazzle camouflage was not to conceal a ship, but to foil an enemy’s attempts to accurately calculate its range, heading or speed using optical observations.  The original “dazzle” as credited to British artist Norman Wilkinson was very blunt, to serve a purpose.  Later the term would be applied to every type of concealing paint job put on a ship, whether that resembled cubism or not.

Below the dazzle pattern helps foil a potential torpedo’s firing solution by misdirection of the ship’s actual heading.

* In the 1860’s the state of the art for aiming a large cannon was to look down the barrel and fire point blank.  In following decades, longer shots at sea were accomplished by guessing a range and then elevating the barrel beforehand while waiting for the sea swell to bring the target into the aim of pre-adjusted iron sights.  Concurrent with the Spanish American War, ships began to be equipped with optical rangefinders invented by Admiral Bradley Allen Fiske.  His stadimeter was a handheld device that looked similar to a sextant and which would later be incorporated into almost all submarine periscopes.  Versions of his coincidence rangefinder that worked by triangulation and trigonometry would quickly find their way into all warships and land based artillery units.  Radar (RAdio Detection And Ranging) was still in its infancy at the beginning of WW2.  In a few short years radars were incorporated or retrofitted into the latest British and American fire control systems aboard ships.  At first radar just augmented either the huge (long baseline) coincidence or stereoscopic type optical rangefinders.

 

  In WWII the paint jobs on ships were looking very different, but the name dazzle still stuck. The famous German battlecruiser Scharnhorst shown above right mimics a smaller, less threatening ship from a distance.

 In the split picture below an unknown warship hides against the bank or cliff side.  The battleship Tirpitz (sister ship to the Bismarck) spent much of the war hiding in such a way.  The cruiser on the right side has a bow wave painted on its front, making it appear to be traveling much faster than it might be.

The catchall “dazzle camouflage” phrase is still being applied to some new warships and face paints today.

The once very popular Argus C3 camera used a stereoscopic rangefinder to focus its lens. Cameras with SLR (Single Lens Reflex) mechanisms would eventually overtake the rangefinder sort, a possible advantage being superior performance at close up distances.

Yet another version of dazzle is CV Dazzle, created by artist Adam Harvey.  CV stands for Computer Vision and his concern is resisting the quickly growing surveillance state that tracks people’s moment with digital cameras and facial recognition software.  The anonymous people behind this intrusive surveillance, be they law enforcement or employees of a private company – just take what imagery they want without asking.  Facial recognition software has grown quite sophisticated recently.  Analyzing how these algorithms work so that they might be countered or thwarted might be good subject mater for a future post.

---

* Now that some established examples of camouflage have been shown 
and the topic outlined a bit; it comes time to introduce some 
ideas that might improve new camouflage schemes for the future...

Op Art

Op Art (or Optical Art) uses optical illusions.  Op Art is abstract, employing perhaps only black and white lines to create an impression of movement or to conceal another image.  Some optical illusions can occur without man’s help, when our physical environment can distort what we perceive, perhaps by bending light.  Atmospheric conditions might be responsible for mirages, for the moon to seem bigger than it should, for far away mountains to appear closer than they really are or for a straight stick to appear bent when you see part of it dip below the surface of water.  Another category of distortions, ambiguities and paradoxes of perception can be caused by physiological activity in the retina of one’s eye.  Afterimages that might linger in one’s vision after he looks away from a high contrast image is an example of physiological optical illusion which is caused by photochemical activity in the retina.  In the so-called  “Hermann grid  illusion” (from German physiologist, Ludimar Hermann /1870) a person probably senses black dots where they don’t exist – because the separate light and dark receptors of the eye are scrambled and are competing with each other for attention.

The most common types of optical illusions may involve neither biology of the eye nor altered perceptions caused by natural environmental factors.  Instead, because of the way the human brain is connected and conditioned it is capable of making very quick assumptions and then of sometimes jumping to false conclusions.

 

“Impossible objects” are two-dimensional figures that can be subconsciously interpreted as three-dimensional objects.  Impossible objects are not physically rational but they can be drawn.  The ‘Penrose stairs’ and the ‘Impossible Triangle’ shown above were both originally thought up and published by a British psychiatrist and his physicist son in the 1950’s.  The Dutch graphics artist M.C. Escher would later incorporate the impossible staircase into some of his work.

Geometrical illusions would appear to distort reality when they actually don’t.  Many are named for the physiologist or psychiatrist who originally created them.  Some simple examples would include the Müller-Lyer illusion, the Hering illusion, the Zollner illusion,  and the shifted-chessboard illusion originated by German-American psychologist Hugo Münsterberg.  Completely different but still a “geometrical illusion” is the  checkerboard illusion (and here is a dynamic HTML version) .

Ambiguous illusions can offer more than one valid perception or interpretation.  The “Necker cube” is an old ambiguous illusion that dates back to 1832 and a Swiss crystallographer (someone who studies atomic arrangements in crystalline solids) by that name.  Around 1915 the Danish psychologist Edgar Rubin created the first ambiguous or reversing two-dimensional form to be called – a “Rubin’s vase”.  Four such vases are shown below.

Hybrid illusions can be perceived in more than one way, depending upon viewing distance.  These illusions can be created by superimposing blurred elements of different photographs over one another.  The technique was originally proposed by Aude Olivia and Philippe Schyns in 1994.  One image dominates up close but another takes over as you step back.

 

 

 

Shadowing plays a very important role in “peripheral drift illusions“.  Reversing the shadowing reverses the rotation of drift.  Strong contrast, blinking, eye movement, peripheral vision and the brain’s perceptual processing contribute to the illusionary sensation of motion.  The almost famous “rotating snakes” image below was copyrighted in 2003 by Akiyoshi KITAOKA, Professor, Department of Psychology, Ritsumeikan University, Kyoto, Japan.  The professor has drawn many other illusions which are also displayed on his website.

Working with similar tricks, the false spiral or twisted cord illusion does not appear to move.  In 1908 a British psychologist named Sir James Fraser drew the first false spiral, where the arcs are actually a series of concentric circles.

Pinna’s Intertwining Illusion is a derivative of the twisted cord illusion.

* Only a few methods of optical illusion have been shown here.
 These toy with either physiologic or psychological mechanism.
 One can better now hopefully perceive, how optical illusions
 when incorporated into camouflage patterns – might help
 enhance the disruptive affect of those patterns.
 

 

Holography, Lenticular lenses, Agamographs & Stereoscopy

Real holograms reproduce very realistic 3D renderings of objects but both the recording and the viewing require laser light.  The hologram itself is a surface profile of the light field surrounding an object.  There are some techniques available to mimic the 3D effect of holograms though.  Lenticular lenses for instance are glass or plastic lenses, textured with ridges or rows of bumps.  In lenticular printing, two or more images are interlaced together on a paper or substrate and then bonded to the base of the lenticular lens.  Either the result looks 3-dimensional or a separate image altogether appears when the viewer observes from a different angle.

Working on a similar principle as the lenticular lens are “Agamographs” which are named after a noteworthy artist named Yaacov Agam.  While Agam made sculptures or artworks from various materials, anyone can create a facsimile of a 3D image by folding paper in a special way and painting segments of different stereo images on alternating folds.

Stereoscopy is stereoscopic imagining and there are a few different ways to do that.   Stereoscopes are the contraptions that you look into to see a three dimensional image with realistic depth.  The left and right eye are segregated to see slightly different vantage points of the same object and then the brain’s visual cortex combines the binocular disparities to produce depth perception.   A typical stereograph consist of two photographs that were taken simultaneously by a special camera that uses two lenses and two sets of film.  A “stereogram” once meant the same as stereograph.  Now however stereogram is synonymous with “autostereogram” – which is a single 2D image that can be perceived as a 3D image, without the help of a stereoscope or use of two images.

Autostereograms depend upon the difference or binocular disparity between two good eyes to create a 3D impression.   Computer software is used to map depth coordinates obtained from one form – to the surface of another image.  Some of the pixels of the surface image are shifted according to the depth of the hidden form.  Most autostereograms are intended to be viewed by means of “wall-eyed convergence”, which means the viewer stares through the graphic, not crossing his eyes.  Visual neuroscientist Christopher W. Tyler with the help of a computer programmer, created the first autostereograms in 1979.  However a simpler form of random-dot stereogram technique was being discussed 60 years before that.

Projection and Perspective

  It could be mentioned that for artwork or mechanical drafting, there are many ways to project a three-dimensional object onto a two-dimensional surface.  First, a 3D projection will have lines of sight or projection lines that are either in perspective or are in parallel.   Perspective in a drawing is where lines converge or skew towards one or more vanishing points.  The lines of parallel projections however, don’t converge into the distance.  Oblique projections slant or slope and have no perpendicular nor parallel relationship with any line or plane surface.  Axonometric projections have lines of sight that are perpendicular to the plane of projection.  Axonometric drawings also have edges or axes that are measured to scale but any curves or diagonals will be optically distorted.
  When architects or engineers want to whip out a quick sketch of a building or object they might resort to a simple parallel/axonometric drawing known as an isometric projection.  The angles in isometric projections are all multiples of 30 degrees.  A draftsman that still knows how to hold a pencil might use a drawing aid known as a 30-60-90 set square, or might sketch on isometric graph paper where the lines are already marked.  Less often used, dimetric and trimetric projections look similar to isometric axonometric projections but use different angles.

Infrared light

In previous decades the thermal imaging night vision equipment that soldiers might have used, worked within the invisible long wavelength infrared (LWIR) or mid wavelength infrared (MWIR) spectrum. These worked by reading the heat emitted by the object itself. Today’s higher generation / newer tech night vision equipment though, uses the ambient IR sent from very distant stars.

These newer night optics predominately rely upon lower wavelengths and higher frequencies; either from the short wavelength infrared (SWIR) or near infrared (NIR) spectrums. These optics produce high resolution images by reading absorption characteristics returned from a target.

Different substances have different IR absorption characteristics. There are many materials that absorb IR, less that reflect IR, some that are transparent to IR and even some materials under development for the influence they might have on infrared light. Some textiles, nets and miscellaneous surfaces used by the military, already dabble with coatings intended to affect visibility in the IR spectrum.

 

Invisibility

There has been some real research done and authentic videos showing how invisibility cloaks could work, but also some false videos about invisibility cloaks – using Hollywood style “blue screen” techniques and video editing software.  The authentic research has a long way to go before the technology could ever be used in a camouflaged suit however.

The invisibility videos that are honest, must still be carefully staged.  The demonstration or illusion if you prefer requires a computer, a video camera, a retro-reflective material, a projector, an iris diaphragm and a beam splitter.  Typically a person stands behind a blanket of special fabric and you think you can see through him; because a camera is filming the scene behind him as a projector puts that same image on the blanket.  The smaller details are complicated.

Metamaterials that can bend light are under development too.  These also have a long way to go before becoming physically practical as a means of concealment.

stencil project

In the slideshow that follows a prospective pattern using some isometric angles and a few circles, was quickly colored in using four colors.   Ostensibly for painting something small like a toolbox.  The original intention was to study how difficult it would be to design a pattern which would comfortably replicate itself over a larger area, once its stencils were moved adjacently up or down or sideways.  Not an elementary task.  Considering that the base-coat of an item will already be of one color, only 3 stencils would need to be cut out with an X-Acto knife.  This is just a disposable example.  The components are a bit too numerous and sometimes too close together to leave behind a sturdy stencil once the holes are cut out.  After re-reading this post the last slide in the series features a little “disruptive shadowing”, added as an afterthought.

This slideshow requires JavaScript.

Pigments, Paints & Dyes

Today volumes and varieties of premixed paints are easily purchased in stores, but this has not always been the case.  Our predecessors just a generation or two prior had to make their own paints, whether intended for a house or barn, or for art.  Right up into the 1930’s or 40’s in construction, paint was made on the job-site and the contractors had to apprentice for many years before becoming competent and considered qualified to make quality paint.  The accomplished fine art painters or masters of yesteryear were akin to alchemist and their materials were varied.  Simultaneously however, many unskilled but ambitious artist may have watched their creations crack, change color or literally slide away from the canvas.  While premixed oil paints were being sold in little squeezable tubes by the 1860s, the knowledgeable and adept artist still depended upon the ability to grind his own pigments and mix his own paints.  With a little know-how it is actually easy to make a decent paint, in most any color.  Cro-Magnon cavemen mixed metallic oxides with tallow or clay to make paints that are still clinging to some stone walls today after thirty six thousand years have passed.  Our repertoire of pigments and binders has grown since then.  An attempt will be made here to organize and explain some basic binders, pigments and dyestuff.

This slideshow requires JavaScript.

* Visiting cave paintings briefly;

   The elements are in a constant state of flux. The erosion and the degradation caused by mother nature is very rough. Any artistic medium must be robust to survive even a decade.  These cave paintings and sculptures of the long since past have only survived because they were sheltered and protected.  Most of the cave art in Europe created during the last ice age has probably been destroyed as a result of successive human activity.  Continued human habitation within a cave would lead to increased smoke and soot. Excessive carbon dioxide from both fire and human breathing might have encouraged detrimental lichen and mold growth upon the cave’s interior. Those caves today that still possess clear aurignacian or gravettian period cave art, do so because they became sealed off somehow from the outside atmosphere. The early humans that painted the pictures seldom if ever lived in those particular caves where cave art has survived. Multiple painters over a wide span of time created the artworks in these caves. Three of the most prominent caves in Europe still possessing pristine parietal paintings were just recently (analogous to their age) re-discovered. The Cave of Altamira in the north of Spain was found in 1879. The Lascaux Cave in the southern half of France was found shortly after the German occupation of France in 1940.  The Chauvet-Pont-d’Arc Cave of south France was re-discovered only in 1994.  These have all been sealed off again, as protection from outside atmosphere and from contamination by human tourism. Pablo Picasso who in 1948 visited the Lascaux cave before it was closed to the public, praised the prehistoric art; stating that man had learned nothing new since then.

The principle colored pigments used in the Lascaux cave for instance were the iron oxides or hydroxides known as hematite, goethite and ocher. Black pigments were provided by magnesium oxide and charcoal.  European cave paintings, engravings and sculptures are grouped together or classified as “Franco-Cantabrian” art because of their geographical concentration inland, both east and south of the Bay of Biscay.

Paint

It usually takes only two or three items to create a paint; a binder, a pigment and a filler.  Any particular paint is classified by its type of binder that in turn is reduce-able by a solvent.  Binders hold pigments and fillers together and onto surfaces.  Pigments can come from plants or animals, from dirt or rock minerals or they can be chemically synthetic.  Fillers if present might influence the opacity of a paint but mainly are added to expand or extend a paint’s bulk and coverage without affecting its color.  When comparing an oil, a tempera or an acrylic version of paint; these might all share the same exact pigment but differ only in having incompatible binders.  The chemical sophistication of modern day automobile paint mixtures are perhaps no more confusing, nor are more complex than some of the mixtures used on the pallets of the late Renaissance painters.  A host of toxic materials like arsenic, chromium, lead, radium and uranium were once commonly used in paints because they were effective.  Commercial house, furniture and spray paints today are usually less convoluted than the compounds once found on an artist’s pallet.  There, one may have found rarefied distillations of tree sap, rabbit skin glue, raw egg yoke, crushed up bug juice or perhaps even pulverized mummy remains.

Binders

The binder dries to form a film that then determines the texture, flexibility and permanency of paint.  Children like to taste things.  Naturally they put things in their mouths as they explore the world about them.  Many effective, once popular binders (or pigments as well) have been removed from commercial paints for this very reason.  Child safe paints, most of which can be produced at home anyway would include binders composed of glutinous grain starch (from rice, rye, wheat flours, etc), soap, shampoo, gum Arabic, shaving cream, gelatin, clay, honey and maple syrup.  Example paint binders not fit for consumption would include things like tallow, linseed and tung oil, shellac, raw egg yoke, beeswax, water glass (sodium silicate), acrylic, epoxy resin, alkyd resins and nitrocellulose lacquer.  A solvent is usually needed to thin out paint, to clean equipment or to clean up spills.  Some example solvents would include “the universal solvent” (water), alcohol, ether, essential oils, turpentines from plants, mineral spirits from coal tar, naphthas like benzene, toluene and xylene from petroleum.

_ Casein is an ancient paint binder and glue, one originally used by the Egyptians, then the Romans and eventually by everyone else.  Made from a milk protein (itself called“casein”) casein forms an excellent, strong woodworking glue or fine paint binder.  Casein is one of the strongest glues known, with a longish working time (2-8 hrs).  It dries hard, veritably permanent and waterproof.

Used thousands of years ago in “distemper” (where egg yokes are excluded) paintings, more recently casein paint was also actually the favored medium for many modern illustrators right up into the 1960 s.  Then new convenient acrylic paints replaced casein bound paints in popularity, mainly because mixed but unused milk based paints would begin to spoil after a few days.

Casein paint is brittle and thus not suitable for flexible surfaces.  It has been used frequently though as the grounds of an artist’s canvas – that first treatment to a porous, absorbent textile fabric stretched over a wooden frame.  It works well on wooden and leather surfaces and walls.  For high wear surfaces like furniture “milk paint” should be protected by a layer of varnish or shellac.  Casein emulsifies well with many different painting mediums including: other glues, gums, oils and resins and varnishes.

For centuries moisture resistant casein glue has been used in laminated woods and for bonding furniture.  Even today some of the higher grade quality laminates and plywoods are made with casein mixed with added resins.  In America, manufacturing interest in forgotten casein glue was rekindled and reborn around 1917 when they began making military aircraft for WWI.  Years later some WWII aircraft like the wooden De Havilland Mosquito still relied upon dependable casein glue to hold their frames and monocoque sandwich shells together. << see replacement by Aerolite & urea-formaldehyde >>.

Casein immersed in formaldehyde created one of the earliest synthetic plastics.  Wooden beer barrels were frequently lined with casein to protect against alcohol corrosion and mould attack.  Some special papers and card stocks are still strengthened and surface hardened by applications of casein.  Commercial casein in bulk powder or flake form is purchased by companies wishing to bind books or stick labels on bottles.

Casein glue is milk protein (which comprises about 3% of whole milk or 1/3^rd of the dry solids in milk) dissolved in an aqueous alkaline solvent.  Making the glue or binder can be nearly identical to making homemade cheese.  Producing a simple casein glue or binder involves little more than causing milk to curdle by introducing vinegar under mild heat, pressing out the excess whey and then neutralizing the acid with an alkali solution (like baking soda and water) with a little more heat.  Non-fat milk makes better glue than whole milk would because fat molecules prevent the casein protein from properly polymerizing.  Low-fat cottage cheese is already converted to curds so it works faster than milk.  The type of alkali used, substantially influences the properties of the final glue or binder.  Alkali s like ammonia, baking soda, borax (sodium tetraborate), ammonium carbonate (originally acquired by the destructive distillation of red deer antlers or “hartshorn”), potash (potassium carbonate) and lime ( either “quicklime” (calcium oxide) or “slacked lime” (calcium hydroxide)) have all been used to engineer casein glue and paint binders.

Either quick lime or slacked lime will work well for casein paints which need to be alkali resistant for applications like stuccoed walls or fences. The “fresco” below was done by a Minoan painter sometime between 1600 and 1500 BC.  It’s holding up fairly well..

Minoan Bronze Age fresco

When you mix cellulose with lye and heat it you get a mild but useful glue known as methyl cellulose.  Methyl cellulose can be used as a lubricant, an emulsifier, gel, as an additive for food, shampoo and toothpaste, as an additive to mortars and gypsum related construction materials and as a binder for medications, wallpaper paste, liquid paints and in dry pastel crayons.

  Hide glue and the gelatin we often eat in some processed foods are both made from an animal protein known as collagen.  It is soluble only in water and therefore is insoluble in oils, alcohol or other organic solvents.  Hide glue is typically made from animal hides and perhaps hooves, tendons and bones (bones are cured in a lime slurry for a couple months before being boiled in water and then reduced).  The hide liquor can be further processed by drying and then by crushing it into chips, flakes or powders that are intended to be re-constituted with water at a later date.  A little heat is necessary so that the re-hydrated binder can be converted from a gel to a liquid before it is applied.  It does not store well in wet form and unused portions will mold.  Hide glue is the preferred glue used for stringed instruments like violins and cellos.  The wood in these delicate instruments is under stress and will expand or contract according to humidity, temperature or external pressure.  Hide glue when dry is appropriately flexible and weaker that the wood it is bonded to.  If a violin is stressed to the point of breakage then the glue bond should break before the wood does. Ideally the instrument can be easily fixed.  This is a handy feature considering that some 300 year old Guarneri del Jesu and Antonio Stradivari instruments can fetch more than $16 million at auction.

Usually animal skin glue is used to prepare, pre-coat or seal a ‘support’.  In the world of ‘fine art’ a support is the substructure of a painting – like wood, paper or stretched canvas.  The ground is the foundation, that first layer of primer painted upon the support.  The size is necessary only for fabric supports and it is painted on above the ground to plug up and and seal the canvas from the penetration of oils. Linen and cotton will prematurely rot without a size layer.  Many sizes have been used but rabbit skin glue was the most conventional ‘size’ used for oil painting and was supposed to be a bit stronger, more elastic and slower to gel than other hide glues.  If used for a ‘size’ then rabbit skin glue was usually mixed with gypsum, marble dust and titanium dioxide to create traditional white ‘gesso‘ sizing. Since climatic changes in temperature and humidity can cause old oil paintings to crack, poly vinyl acetate has become the preferred binder in contemporary ‘gesso’ or ‘size’ for fabric supports.  Fish glue or “isinglass” (made from air bladders, boiled skins and fish bones) was used by the ancient Egyptians and was later prevalent in the parchment manuscripts illustrated and gilded by medieval monks.  Fish glue was one of the more successful fixatives used in pastels, where pulverized pigment, white chalk and binder were commonly rolled up into a cylinder before they were dried.  Today isinglass is still useful as a “fining agent” for the clarification of some wines and beers.

* Tempera, Distemper, Encaustic and Fresco painting:

   Casein and hide glue have been used since antiquity to bind up and apply pulverized pigments.  The term “tempera” has often been used to casually imply several mediums (like egg, honey, plant gums milk casein and hide glue) though.  To most artist today “tempera” implies a technique employing only the egg yoke medium, and they might use the new term “distemper” to differentiate and encompass the other binders used in a similar way.  Tempera painting is very old and robust and was very common before “oil paints” became popular in the 15th century.  Some examples of tempera still exist, which were painted almost two thousand years ago.  Egg tempera dries very quickly so usually a bit of wine, vinegar or water is added to extend its period of workability.  Also about 2,000 years old, “encaustic” painting is a technique where pigments are added to melted beeswax.  Metal tools, special brushes and heat are used to spread the pigmented wax around before it solidifies.  “Fresco” (meaning fresh) is a technique where pigment is applied onto wet plaster.  The hue is drawn into and becomes part of the wet plaster itself after it is applied to ceilings, walls or murals. “Fresco-secco” on the other hand describes painting upon dried plaster.  The famous ceiling of the Sistine Chapel taken as a whole, is an enormous fresco painting done by Michelangelo about 500 years ago.

This slideshow requires JavaScript.

  Silicate mineral paints are made from mineral pigments and soluble glass as the binder. “Water glass” (sodium or potassium silicate, liquid glass or Keimfarben) is made by melting silicon dioxide (silica / quartz sand) and soda ash (sodium carbonate) together.  The result is an exterior masonry paint binder or indoor product for mural painting, that is far more resistant to cold and damp and ultraviolet light than traditional lime fresco is.  Keimfarben was popular for a while as a 19th century variation of fresco, and remains useful today as a coverage for concrete and masonry walls.  Other uses for sodium silicate include its use as a paper glue in the manufacture of cardboard, as a tool for water treatment, as a fixative for reactive dyes, as a binder for refractory mixes and as a major component of dry-powder laundry and dishwasher detergents.

Oils

Some of the most important binders of all time are the so-called “drying oils”. These are the foundation of oil paints. When exposed to oxygen these particular oils have the property of polymerizing into the hard films we associate with dry finished, cured paint.  Linseed oil and tung oil are the most significant examples in this category but there are others less frequently used like poppy oil, soybean oil, castor oil, candelnut oil and so on.

  Linseed oil is squeezed from the seeds of the flax plant.  Flax seeds are edible and the fibers from the plant are probably the longest ones to be found in the textile industry.  Linen is the fabric made from flax fibers and both ancient Babylonians and ancient Egyptians cultivated the plant.  Raw linseed oil is edible but it does not dry or oxidize very quickly.  Therefore a quicker to dry “boiled linseed” was realized by experimentation.  In the 19th century additives like lead acetate and zinc sulfate were introduced to raw linseed oil and then heated, to improve the drying performance of the oil.  Today the heavy metal driers (perhaps cobalt & manganese salts) of boiled linseed oil may have changed to ones safer to handle, but boiled linseed is still not safe to eat.

  Tung oil (or Chinese wood oil) usage reaches way back before the Song Dynasty in China. The oil is squeezed from the nuts of a poisonous tree. This oil was or still is used for waterproofing wooden ships & paper umbrellas and for providing light when used as a lamp oil.  Modern day granite and marble counter-tops can be waterproofed and made stain resistant by thinned coats of tung oil.  Tung trees were once imported to the southeastern U.S. and planted as commercial crops.  Since that time the prolific and toxic trees have been classified as unwanted and invasive plants in states like Florida and Mississippi.  There have been incidents where school children on field trips have been poisoned after mistaking tung nuts for chestnuts.

Both linseed and tung oils make superior wood finishes that penetrate deep and rejuvenate cellulose.  Tung oil which is more expensive, may or may not be preferable in some situations because it is less likely to darken wood or to yellow.  Tung oil will eventually harden or polymerize by itself but boiled linseed preforms much faster – making linseed by far the most common drying oil employed in oil paints.

* Linoleum is a superior type of non slip floor covering made with linseed oil, which was invented around 1855 and became very popular by the beginning of the 20th century.  Being more flexible than ceramic tile, it could be applied to wooden floors and not crack under stress.  The thick inlaid linoleum floors were extremely durable but eventually thinner, printed pattern linoleum tile was manufactured.  Still this thinner linoleum flooring should be preferable to the cheap polyvinyl chloride (PVC) floor covering so popular today.  Simple enough to make at a remote construction site, linoleum fabrication usually began with a burlap or canvas backing.  The obligatory ingredients for linoleum tile were fine sawdust (or wood flour) linseed oil and some color pigment. Occasionally pine rosin and calcium carbonate (crushed limestone / as an extender) was thrown into the mix.  In fact, calcium carbonate (occasionally called whiting) is often used to extend or to fill in many types of paint, plastics and thermosetting resins.

Gums

Gums, resins, turpentines and essential oils come from plants and whether mixed to together or used separately they still have been used as paint binders for hundreds or even thousands of years. “Gums” for example result from “gummosis” which is a condition of sap flowing from a wound or disease in a bush or tree.  Gums are colloidal (a mixture in solution that does not settle) and are soluble in water while simultaneously being insoluble in alcohol or ether.  Resins may occur either alone or alongside gums and essential oils but they are conversely – insoluble in water but are dissolved by alcohol and ether.  Then there is a large group of harder resins called “copals”.   Amber which is a petrified tree sap, falls into this category.  Oleoresins are solutions of resin or wax mixed with essential oils and fatty oils.  Turpentine is an oleoresin collected and distilled usually from pine tree sap.  Balsams are like oleoresins but are generally more aromatic and occur naturally.  Essential oils are the fragrant, volatile compounds from plants, usually extracted by distillation.

Confusingly gum arabic and Arabic gum are two very separate but famous and important tree saps.  The natural gum and polysaccharide “gum arabic” comes from the hardened sap of select acacia trees.  “Arabic gum” (or mastic) on the other hand is resin collected from a totally unrelated dioecious shrub of the Pistacia (pistachio) family.  Both resins were known in antiquity, both were used in foods, as medicines, as paint binders and both still share great value as precious commodities.  A major portion of the world’s supply of gum Arabic comes from Sudan while most mastic comes from a small island, farther northwards from the equator.

Gum arabic is composed of saccharides and glycoproteins which give it the utility of a glue and paint binder and make it edible by humans.  Thousands of years ago the Egyptian Pharaohs were being mummified with the help of gum Arabic.  It is the same useful glue used on the back of a postage stamp, which is licked before sticking to an envelope.  It is used in cosmetics, shoe polish, candies and chocolates, to treat upset stomachs or to stop both diarrhea or constipation.  Gum arabic is indispensable in traditional lithography, paper and textile printing, where it controls viscosity in inks or repels ink from background areas on the plate of an offset press.  “A dab of gum arabic makes newspaper ink more cohesive and permanent”.   In medicine, gum arabic is used as an emulsifier to keep ingredients from separating or as a demulcent to temporarily defend the mouth, lips, tongue, eyes or nose from irritation.  It is used in glazes and paints, particularly in watercolors where it binds pigments to paper.  Gum arabic literally holds the multi-billion dollar soft drink industry together.  Without its ability as an emulsifier, the sugar in a ‘soda pop’ would crystallize and settle to the bottom of its container.  The economic importance of this tree sap has been influential enough to sway national policy.

Mastic or ‘Arabic gum’ was once worth its weight in gold.  It has long been collected from the sap of the Pistacia lentiscus shrub which is mostly cultivated on the Greek island of Chios.  Once dried in the sun the resin could be used as a chewing gum.  The English word “masticate” stems from an original Greek verb for chewing.  Mastic has antibacterial and anti-fungal properties that may counteract gingivitis and tooth decay.  Mastic also contains antioxidants and has traditional been used in medicine.  Just like the gum collected from Sudanese acacia trees, mastic is used to make cosmetics, incense, perfumes, soaps and lotions.  Transparent varnishes made with mastic were once very useful in preserving photographic negatives.

Resins

In the English language the term “resin” it too vague.  A resin usually denotes a highly viscous organic residue and a residue that often solidifies after contact with air.  Within the plant a resin might control water loss or act as an antiseptic. “Oleoresin” is a broad term for compounds collectively containing resins and oils (like turpentine).  At least two different types of oil are distinguished: fatty oils (containing fatty acid chains, lipids, triglycerides and such) and essential oils – which contain volatile aromatic compounds.  A “balsam” isn’t distilled but is an aromatic oleoresin that occurs naturally.  “Copal” was originally a semi hard tree sap used as incense by the natives of Central America, now it is a catchall phrase for similar resins that make good hard elastic varnishes.  Copals can be dissolved by oleoresins, by essential oils or by acetone; but to do so sometimes requires the application of heat.  Amber is a rock, a fossilized resin and the hardest copal.  Rosin is a resin usually collected from pine trees.  Rosin is what is left over after turpentine has been cooked and separated from pine tree sap.  After destructive distillation the leftover solid is ground up into a powder.   Rosin is used in adhesives, soaps, soldering flux, optical lens polishing compound, etching plates in printmaking and in oil paints and tempera emulsions of fine art.  It sees employment as a traction or friction enhancer used by rock climbers, weight lifters, bull riders, gymnast, ballet dancers, violinist and cellist alike.   There are many other plant gums or resins used as binders or glazes in paints.

Also found or even predominant in modern paints are thermosetting and thermoplastic resins.  A “thermoset” or thermosetting polymer is at first soft or liquid, malleable or mold-able before it is irreversibly cured or “set”.  Once hardened, heat cannot be used to change a thermoset’s shape.  Examples of thermosetting resin include Bakelite, epoxy resin, vulcanized rubber, polyurethanes and polyester resin and silicone (the rubber like adhesive and sealant, not the chemical element silicon).  Thermoplastic resins on the other hand are often formed to shapes by injection molding or extrusion molding, but once cooled are still quite modifiable in shape by the reintroduction of heat.  Example thermoplastics include acrylic, nylon, Teflon, polycarbonate, polyethylene, polypropylene, polyvinyl chloride and polystyrene resins.

*  Distillation is used to divide mixtures into separate components.  Destructive distillation (pyrolysis) uses heat to drive off valuable liquids and “volatiles” from organic material.  The organic material’s original form is lost, its molecules cracked, reduced or rearranged into new compounds.  Charcoal, methanol, tar and turpentine are gained by the destructive distillation of wood. Coal gas, coal tar, ammonia and coke are gained by the pyrolysis of coal.  Dry distillation is a case where gas is driven off from a heated solid and is then condensed and collected.  Mineral sulfates treated this way resulted in sulfuric acid when the gasses were absorbed by water.

*  Distillation of crude oil is preformed in an enormous type of still called a fractionating tower or column.  In such a tower the lightest and most volatile “fractions” are the first to rise to the top after the application of heat.  The liquefied petroleum gases such as butane, propane, propylene, butadiene, butylene, isobutylene are the first products to be removed and collected.  Next, in order of their vapor pressures; gasoline, naphtha, kerosene, diesel and fuel oil are separated.  An important phenomena occurring within such a column is “reflux”; an action where condensed vapors (liquid now) fall back down through the column, enriching rising vapors as they drop. 

*  Steam distillation is useful to extract many organic compounds that might otherwise be destroyed by the high temperatures in a normal retort still or reflux column.  With steam distillation, water vapor lifts vaporized particles from the mass and transports them to the condenser.  In effect the desired products are less damaged because distillation occurs at lower temperature.  Newer and more effective than steam distillation is vacuum distillation which lessens the pressure above the liquid mixture, effectively assisting in the quick evaporation of the lightest volatiles. 

Tiny amounts of essential oils can be extracted from plants by steam distillation or by solvent extraction.  Essential oils are the “essence” of a plant’s fragrance.  They are a concentration of ‘volatile aromatic compounds’ which are in effect only small molecules that change physical state from a liquid to a gas very quickly.  Volatile aromatic compounds move through the air quickly to stimulate the olfactory sensors in our noses.  Essential oils are used in medicines, foods, cosmetics, soaps, cleansers and perfumes.  They are frequently contained within oleoresins.

Lacquer, Shellac and Varnish

In general, lacquers are differentiated from paints by virtue of being more glossy.  The word “lacquer” is derived from the lac insect and a Sanskrit word for the number 100,000.   Millions of these little insects are cultivated for the purpose of secreting a resin that they produce after sucking sap from a tree.  “Shellac” (mostly coming from India) is the filtered and refined bug resin that makes such a useful wood finish and dye for both fabrics and leathers.  There is also a long established lacquer in the orient which is extracted from the Chinese or Japanese “lacquer tree” (Toxicodendron vernicifluum).  This tree sap which turns into a strong safe clear film once dried, actually contains the same poisonous irritant as “poison ivy” and therefore is difficult to work with when wet.

One or two centuries ago westerners tried to imitate the effect of Oriental shellacs and lacquers with what are called “varnishes”.  Omitting synthetic alkyd and polyurethane examples, the best (natural) varnishes came from dissolved copal resins.  Varnishes can be categorized by the type of solvent used.  ‘Spirit varnishes‘ for instance usually use alcohol as the solvent, but occasionally employ naphthas (the lighter liquid petroleum fractions) also.  Certain resins when mixed with these solvents dry fast and hard.  The film may stay clear (does not yellow with age) but the “spirit varnish film” is thin and brittle and not very durable.  ‘Essential oil varnishes‘ will use a heavier solvent like turpentine mixed in with the resin.  While this makes a tougher film than spirit varnish, it may take a long time for the solvent to dry.  Finally the ‘fixed-oil varnish‘ employs a resin mixed in with a “drying oil” like linseed oil. This makes the toughest, thickest most durable film or varnish of all.

   Latex paints might use water soluble acrylic resin, vinyl acrylic or styrene acrylic as binders.  White glue (like Elmer’s ® glue) that children soon become familiar with is actually polyvinyl acetate (PVA or “caparol”) and has the same composition as cheap latex paint.  There is no real latex in ‘latex paint’ actually.  “Latex” should denote natural rubber extracted from a jungle tree, not a synthetic polymer.  Acrylic resin, vinyl acrylic (PVA) and styrene acrylic bound paints are erroneously called latex in the U.S., but their called “emulsion paints” in the UK.  Their chemical composition is complex and far beyond the capability of the average person to replicate.

*  Acrylic resin is about twice as expensive as vinyl or styrenated acrylic.  A typical interior ‘latex paint’ contains about 20% acrylic and 80% vinyl.  Latex paints were unknown before the 1930’s or 40’s.  Prior to that time exterior paints were often made with linseed oil binder and interior paints were often based on milk (casein).  Today’s interior latex should be considered superior in most every way to yesterday’s casein or milk paints.  Exterior latex may exhibit good durability and fade and crack resistance but has not yet completely displaced old fashioned oils.  Here linseed based or alkyd based oil paints are extremely durable themselves and unlike acrylics will often penetrate deeper below the surfaces of wood and rust.  Exterior latex with 100% acrylic binders preform very well though in terms of UV resistance and in alkali resistance when applied to concrete & masonry.  Cheaper, predominately vinyl acrylic latex does well inside where smudges and grime may need to be scrubbed from walls.  Styrenated acrylic latex paint is often used on ceilings; its also good as a concrete or masonry sealer because it resist alkali burn and efflorescence (that situation where salt leaches through to the surface of concrete or another porous material and forms crystals).

   Alkyd paints were invented in the 1920’s, improved upon and used sporadically by some in the 1930’s and were commercialized in the 1940’s.  DuPont produced its first alkyd paints for artist in 1931.  The word “alkyd” (or “alcid”) is derived from the words “alcohol” & “acids”, which are both required to make the polyester.   Alkyds are polyesters manufactured from polyols (alcohols), aromatic acids and organic fatty acids.  Alkyds have become the most common “oil-based” type, premixed paints that are commercially available.  Since alkyds are made from both petroleum and vegetable products they are also reduced or thinned by most petroleum solvents or vegetable oils.

   Epoxy polymers are mixed with complimentary hardeners to produce whats called a thermosetting resin.  A thermoset is at first wet or soft before it becomes hard, insoluble and irreversibly cured.  Thermoplastic polymers on the other hand are pressed or injected into molds using heat.  Epoxy resins are important engineering or structural adhesives but they are more frequently being used as tough paint coatings by industry as well.  The surface paint or a priming undercoat of an automobile may be epoxy resin because of the superior adhesion and corrosion resistance this paint provides for metal.  Many water pipes, rebar (iron bars used to reinforce concrete), appliances like refrigerators, stoves, laundry driers and washers are covered with epoxy powder coat called FBE (Fusion Bonded Epoxy Powder Coatings).  Epoxy coatings are more heat resistant than latex-based or alkyd-based paints but they still deteriorate under UV exposure.  Like both latex and alkyds, epoxy resin was thought up and perfected by chemist rather recently (the 1930s).

  Nitrocellulose lacquer:  Many women paint their fingernails with the same chemical used to make gunpowder.  General Motors began painting automobiles with the lacquer in the 1920’s.  Nitrocellulose (guncotton or collodion or cellulose nitrate) was not the first “high explosive” because “nitrostarch” was discovered or invented about thirteen years before.  The inventions of nirtoglycerin and then dynamite would follow, not precede guncotton.  In 1846 nitrocellulose was apparently discovered or stumbled upon simultaneously by three different chemist working concurrently in separate laboratories.  It was made by saturating plant cellulose (like cotton) in nitric acid.  Nitrocellulose became the main ingredient in smokeless gunpowder and it became a support for photographic film.  It was probably the first plastic, and as a substitute for ivory it was soon molded into piano keys, billiard balls, tool handles and so on.  Nitrocellulose was also used to make the first transparent plastic roll film used for photography and it was used as a binder for tough, glossy automotive paints.

* Before nitrocellulose, nail polish might have been made from a mixture of gum Arabic, beeswax, egg white, gelatin and vegetable dye.

* The most common nail polish remover is acetone but his can be harsh on skin and nails. Sometimes ethyl acetate is preferred and this us usually the original solvent for nail polish itself, anyway.

* Before Henry Ford started making millions of his Model T’s, the other car makers used oil paints to accent their automobiles. As early as 1865 commercial oil paints began to appear that had extended shelf life due to the addition of sodium silicate (see waterglass or Keimfarben above). Based on slow drying linseed or tung oils these other car paints might have taken several weeks to harden. These oil based paints looked good for a year or two until ultraviolet light from the sun began to fade, yellow or dull the color. Ford’s innovation was to develop asphalt-based baked enamels for his cars that were similar to a paint technique called “Japanning”. Japanning is a dark decorative patina or finish acquired by painting a thin layer of bitumen (asphaltum) over an object but allowing some of the original surface to show through. Ford saturated his fenders, hoods and other metal parts with Japan Black (a paint bitumen) suspended in linseed oil and tinned with either mineral spirits or petroleum naphtha. The wooden components used a different paint recipe. Then as Japanned ornaments usually are, the metallic parts were baked in a tunnel oven for about an hour on a separate, slow moving assembly line. At the height of production a new Model T – with paint thoroughly dried – rolled off the floor about every three minutes. Drying time was not the only consideration for Ford, because the black paint job was much cheaper and ultimately more durable than what the competition was producing.

* Pierre DuPont owned stock in General Motors, years before his chemical company developed nitrocellulose paint lacquers. Around 1923 GM hit the automobile market with cars painted in new colorful “Duco paints” (pyroxylin / nitrocellulose based). These paints came in every color of the rainbow and took only minutes to dry. In the 1930’s the first metallic car paints appeared. These used real fish scales at first and eventually graduated to cheaper aluminum flakes. Sunlight resistant clear coat enamels for cars appeared in the 1940’s. The first synthetic polymer / transparent thermoplastic, “acrylic resin” car coats appeared in the 1950’s. These had the advantage of drying much faster than enamel coats. Acrylic lacquers were eventually superseded by what is preferred today, which is usually called a “clear coat finish”. A clear-coat-finish usually consist of a primer, a color coat and a clear, tough, polyurethane topcoat.

Fillers

Fillers are intended to increase and extend the coverage of paint. Fillers are cheap, non-essential components that add bulk and might sometimes influence opacity. Example fillers include: clay, chalk, powdered marble / calcium carbonate, mica, baking soda, plaster of Paris, tile grout, sugar and vinyls like polyvinyl chloride or polyvinyl acetate.

Pigments

Practically any attractively colored earth can be used for homemade pigment.  A good way to process it is to boil a quantity in water for several hours.  Strain out the impurities and larger aggregate and pour off the excess water.  Place the still moist residue in shallow pans and allow to dry.  Grind further in mortar and pestle if possible and sift once more through a finer screen or filter.

Pigments are insoluble color particles that require a binding agent to hold them onto the surface of the material being covered.  The first pigments came from the earth and from inorganic metal oxides.  This limited and somewhat dull spectrum or pallet of colors was eventually broadened and enhanced during the early 19th century.  Some new colors were created then, when mixtures of metal oxides and earth pigments were cooked and fused together under high heat.  Finally, by the end of the 19th century, advancements in a new field of science known as organic chemistry enabled the creation of several intensely vibrant colors.  Modern synthetic pigments, inks and dyes are based upon the carbon molecule and were created in laboratories.  Today almost every natural pigment has been replaced by a synthetic organic alternative.  Modern pigments behave differently, not necessarily better than older mineral pigments in that when mixed or thinned down they generally shift in “value” and not in “chroma”.

Some common earth pigments include green earth, goethite, ocher, hematite, sienna and umber.  Some natural mineral pigments include Malachite, Vermillion and Lapis Lazuli.  Some artificial mineral pigments not found in nature are Venetian Red and Caput Mortuum.   Some organic pigments of natural origin would include carmine, gamboge, Indian Yellow, madder root and mummy brown.  Some synthetic inorganic pigments that are manufactured include Ceruleum blue, Prussian blue and Cobalt blue, Cadmiums and White Lead.  Some synthetic organic pigments (lab created / carbon based) include the azo pigmens, dioxazine, isoindolinones, quinacridones and phtalocyanines.  There are too many pigments with too many details to define them all properly here.  Entire books have been dedicated to the subject. The vast majority of pigments available in the marketplace today are actually synthetic.   A short, far from complete list of traditional, non synthetic paint pigments follows.

– Green Earth is similar to ocher; a mixture of ferrous hydroxide and silicic acid.
– Goethite (Brown Ocher) is a unique mixture of ferrous hydroxide.
– Ocher (usually a yellow) is a clay that contains hydrated hematite (an ore from which iron has been smelted for the last 6,000 years).
– Hematite (usually red unhydrated mineral iron ore) stems from a Greek word for blood. “Limonite” ore comes from the Greek for meadow (meadow/ marsh/ bog ore/ brown / yellow). Ocher then is a catchall phrase for abundant natural earth pigments containing iron oxide and depending upon hydration states and additional ingredients may range in color between yellow, red, purple and brown. The artist and painters of the Medieval and Renaissance period knew how to cook ‘ochers’ with heat to drive away the chemically bound water, achieving unique hues.
– Sienna (usually brown) is a mixture of iron oxide and manganese oxide. Yellowish-brown “raw sienna” is turned into a reddish-brown “burnt sienna” when cooked with heat.
– Umber (both raw and burnt) is also a mixture of iron hydroxide and manganese oxide. It is usually darker than either ocher or sienna.
– Malachite (usually green) is a hard copper carbonate mineral. It often comes from underground stalactites. <pic>
– Ultramarine (deep blue) was originally made from crushed Lapis Lazuli. It was an extremely expensive pigment that was hard to make and it was used sparingly. <pic>
– Venetian Red pigment comes from red iron oxide but it is artificial because it is or was collected from heated chemical waste of manufacture.
– Caput Mortuum (usually purple) from Latin – meaning “worthless remains” was usually collected from leftover, useless iron sulfate (copperas) residues.
– Carmine pigment (crimson or bright-red) is obtained from carminic acid.  Since carminic acid wasn’t reproducible in the laboratory until 1991, it has since ancient times been acquired by crushing up little scale insects.  Polish cochineal and Kermes dyes were both from scale insects and known in ancient Europe and were later valuable commodities in the Middle Ages.  Mexican or Spanish cochineal (from a different, New World scale insect that eats prickly pear cactus) quickly became the preeminent scarlet dye in the 16th century.  Although carmine or cochineal are better known as food colors, lipstick and fabric dyes today, artist like Michelangelo also used them in paints.
– Madder root has been used since antiquity as a (red) dyestuff, but it has also been used for tinting paints. It wasn’t known in Europe until returning Crusaders brought it back to Italy. During the Colonial Period the typical red uniform of the British Army was dyed with madder root, while the officers that could afford it had their own uniforms tailored and dyed with brighter and more colorfast carmine or cochineal dye.
– Gamboge is a saffron / mustard yellow pigment that is obtained from the sap or resin of a tree. It is the traditional color and dye used for the robes of certain Buddhist monks. It is often used in watercolor but is not lightproof.
– Indian Yellow is was collected from the urine of cows that ate mostly mango leaves. It is a natural organic “lake” pigment. Authentic Indian Yellow is quite permanent, very expensive and often imitated.

– Uranium Yellow from uranium oxide; often found in vanadium ore, made a useful pigment before the Manhattan Project found a better use for every available bit of the element in the 1940’s.
– Orpiment (yellow) and Realgar (red) were both popular since Roman times as pigments.  The two pigments differ slightly in chemical composition but both consist of poisonous arsenic sulfide.  Arrow tips were occasionally dipped into solutions of these minerals to make them more deadly.  The minerals were originally found as crystalline deposits nearby volcanic fumaroles and geothermal hot springs.
– Vermillion (bright red or scarlet) comes from the crushed crystal of mercury sulfide known as “cinnabar”.
– Emerald Green was a very poisonous and dangerous pigment made from copper arsenate. By itself it made a durable and attractive pigment but would later turn black if mixed with sulfur colors (like cadmium yellow, vermilion and ultramarine).
– Mummy Brown was a very useful and popular paint pigment made from the crushed up remains of Egyptian mummies. Most artist in the past did not know of its true origin. Perhaps some pigment called mummy brown was produced by burning ‘green earth’. Mummy Brown was still being made in the 20th century until sources of available mummies finally ran dry.
– Asphaltum or bitumen is a brown / black pigment derived from solidified petroleum. It might be used as a binder for gravel and sand in asphalt road surfaces but it has also been used as a pigment. Ancient aboriginal N. American Indians used it to decorate pottery and Henry Ford used it to paint automobiles.
– Ceruleum Blue; a synthetic inorganic pigment made from copper and oxides of cobalt
– Prussian Blue (also Paris Blue or ferric ferrocyanide) was the first modern synthetic pigment. It is a dark blue, non poisonous, iron-cyanide based compound with intense chromatic power. It was the main color of uniforms used in the Prussian Army and was the traditional blue used in “blueprints” (or cyanotypes – which exploited the light sensitivity of paper perhaps, coated with gum Arabic & ferro-gallate (acidified iron) type solutions).
– Cobalt Blue is made from heating together cobalt and aluminum oxide. Some Chinese porcelain pottery has mixed the same minerals for many centuries but blue glass and cobalt blue paints have been used now for about 200 years.
– Cadmiums are very vibrant and light-fast yellow, orange and red pigments made from oxides of cadmium. They are expensive pigments, potentially toxic and superior to modern organic alternatives in almost every respect. <link Europe ban>
– White Lead (or Cremnitz White) is lead carbonate and has historically been the principal white pigment of classical European oil painting. When mixed with a dryable oil it spreads wide and covers especially well and with high opacity. White lead paint was once commonly used to protect the hulls of wooden ships from shipworm. Unfortunately lead paint has been banned in most countries because of its potential toxicity and ‘titanium white’ has replaced it. Lead carbonate is the same substance that forms white crystals on terminals of a car’s battery. Historically the pigment was produced by subjecting lead to the fumes of strong acetic acid <vinegar>. Red Lead paint on the other hand is lead oxide and was once very valuable as an anti-corrosion / rustproof primer paint. For example this primer distinguished and protected the Golden Gate Bridge near San Francisco for thirty years before re-painting became necessary and before the formula was changed.
– Titanium White is titanium dioxide (Ti O2) and is non poisonous. It has great covering power and is bright – with a high refractive index.
– Zinc White is zinc oxide. It is a very useful non toxic pigment developed about 170 years ago that tints less or is more transparent than titanium white.
– Zinc Chromate when used as a pigment was known as Zinc Yellow.  It is not used in art anymore because it degrades quickly to brown and is toxic and carcinogenic.  Zinc chromate does make a very useful paint coating in industry where it is used to passivate (protect from corrosion) metals like tin alloy, galvanized steel, cadmium, magnesium and aluminum.  Metal tools that have undergone a chromate conversion coating usually display a distinctive yellow-green iridescence.

This slideshow requires JavaScript.

Dyes

Again, the difference between a pigment and a dye is that one is soluble and the other is not.  Inks incidentally, can be either dye-based or pigment based solutions.  Paints need a binder to hold little solid particles of color pigment to a surface.  Dyes on the other hand contain infinitesimal refractive coloring compounds that are dissolved in solution.  Pigments are generally better than dyes in keeping their color by resisting damage from high heat, bright light or chemicals.  Dyes can cling to or be absorbed into only a few types of surfaces.  Without special preparations, dyes cannot be turned into the pigments used to color paints.  Therefore a “laked pigment” is one wherein a soluble dye is absorbed by or chemically bonded to a transparent insoluble salt; which then leaves behind a particle of insoluble pigment.  Calcium salts from sources like bones, chalk or white clay were historically the first salts used to entrap dyes for use as pigment.  Today chromium and cobalt metallic salts are more frequently used to manufacture lake pigments.

From ancient times people have been dyeing fabrics and leathers and furs.  Woad, weld and madder are natural dyes that have been used for the last 3,000 years or more.  Today dye chemist are busy designing ever better molecular dyes, for the examination of neurons in a nervous system or to study DNA by examining specific genes.  Other dye chemist might be busy perfecting a contrast dye for use by an MRI (Magnetic Resonance Imaging) machine or inkjet solutions for 3D printing or microcircuitry fabrication.  Here they would need to consider electrostatic properties, solvent compatibility, resistance to bleeding and spreading, consistency and flow properties or perhaps the adhesion of dye or ink to a substrate.

Wool and other so-called “protein fibers” like hair and silk are the easiest fabrics to color with a natural dye.  First the oils on fibers like wool need to be washed or “scoured” away before a dye can penetrate.  Cellulose fibers like cotton, linen, flax, hemp, jute, paper, cane, rattan, etc. are less suited to natural dye uptake and may need to be treated beforehand by a mordant.  A mordant is a chemical used in solution that helps embed color into a fiber.  Taken from a French word that means “to bite” or to take hold, a mordant allows the penetration of a dye into fiber,  similar to the way a laked pigment binds within a crystal.  Some “substantive” or “direct” natural dyes like those from walnut hulls, Tyrian purple from a sea snail, lichens, onion skins, tea or coffee will stain and stick to wool without the help of a mordant, but these might eventually wash out or fade.  Substantive or direct dyes without assistance of a mordant cling to fibers by relatively weak hydrogen bonding.  Other types of dye molecules however can attach to fiber molecules by complicated Van der Waals forces or by ionic or convalent bonding.  The most permanent dyes are fiber reactive dyes that establish strong covalent bonds.

The most common mordants are alum, copper sulfate, chrome, iron sulfate, tannic acid and tin.  Some of the direct dyes already contain a tannic acid mordant (ex: walnut, oak and pecan husk, tea & coffee).  The choice of mordant will usually influence the outcome of the dyed color.  Alum (aluminum potassium sulfate) causes the least change in color.  Copper sulfate (Blue vitriol) sometimes turns fibers green.  It can be collected by soaking dirty old pennys in acid.  Iron sulfate (copperas) “saddens” color and makes them more green-brown or gray.  Historical “iron gall ink” employed iron sulfate.  Copperas can be made by soaking rusty nails in sulfuric acid.  Tin (stannous chloride, specifically) brightens colors, especially reds and yellows, but it can be very harsh on fabrics.

To bring this complicated topic to a shortened end so that this blog post can be published today rather than next month; many details about dyeing will need to be skipped for now.  The goal at present is to explore dyes insofar as they intersect with pigments and paints.  Perhaps this segment on dyes will be amended later.  More time is needed to compress information and to insert little details.  For instance, for forty years following its invention TNT was used only as a yellow dye.  TNT is so insensitive it took that long to find a satisfactory way detonate it.  Poke berries are not commonly used for either dye or ink; but the final draft of the American Declaration of Independence was penned in fermented poke berry juice.

Paint recipes

The Internet is loaded with recipes for children’s paints.  These may contain binders of soap, glue or flour and pigments of Kool Aid ® or food coloring and the like.  One may find a recipe for creating a paint from egg yokes and colored chalk.  { Michelangelo may have used the same tempera ingredients on the Sistine Chapel but since he painted upon wet plaster the work is called fresco, remember }.  Digging deeper one can find recipes more applicable for bulk paints.  There is no need to replicate here, the work already done on another web site.  One decent site providing information for homemade paint is provided by motherearthliving.com.  The following list of ingredients for “Clay paint” is copy and pasted here, as insurance against the possibility of “link rot” in the future.  The paint’s final color would be determined by both the hue of the powdered clay chosen and by any auxiliary pigments added.

CLAY PAINT
1 part wheat, rice, rye, or potato flour
2 parts cold water
1-1/2 parts boiling water
1 part powdered clay
1/2 part inert powder filler (options: mica flakes and powder, chalk, powdered ­marble or silica, 60- to 80-grit sand for rougher surfaces)

Gritty “chalkboard paints” similar in texture and performance to the slate chalkboards found in old school rooms can be created from either commercial latex (emulsion) paints or homemade paints.  One simply adds plaster of Paris, baking soda, un-sanded tile grout or calcium carbonate to the paint.

A simple black paint can be made from potatoes.   Several potatoes are slowly baked in a fire or in an oven until they turn completely black and dry inside.  These are then crushed to a fine consistency and the powder is mixed with linseed oil.  For a useful olive drab (Army green) color one can add yellow ocher pigment.

Considering Leather

The most utilitarian and multipurpose material ever readily available to early man came from the hide of an animal.  Making leather from hides or furs from skins might have been the first human industry.  Until the very recent dawn of plastics and synthetic fibers, leather and fur were nearly indispensable commodities.  Leather is a superior material for several applications like footwear, saddles and upholstery and still remains the material of choice over any synthetic alternative.  However, turning a smelly raw animal skin into usable leather is a difficult process.  Before certain procedural and chemical advancements in the previous century, commercial tanning was even yet a more laborious and time consuming pursuit. This post will endeavor to briefly separate and identify some of the varied techniques used in leather tanning, while perhaps empowering some readers with a few ‘do it yourself’ type leather tanning skills.

What is leather?

A mammal’s skin or hide consist of a thick center layer called the “dermis” or “corium” which is sandwiched between a thinner epidermis on the outside and a subcutaneous fatty layer on the inside.  The corium of a fresh hide contains between 60-70 percent water and 30-35 percent protein by weight.  Of that protein about 85 percent is of a special fibrous type called “collagen”.  These protein fibers are held together by chemical bonds.  Tanning chemicals (tannins, enzymes, acids, bases or salts) in effect alter these bonds between collagen fibers, remove water and dissolve natural fats within a hide.

If a fresh hide can be frozen, salted or quickly dried then it can be temporarily spared an otherwise inevitable decomposition from bacterial rot.  A fresh hide may have a few useful applications in raw form though, considering its tendency to shrink substantially upon drying.  However should dry rawhide be re-hydrated, it immediately becomes susceptible again to rot.  Raw hides have value and those destined for leather processing are soaked in brine or packed in salt at the slaughterhouse before being shipped to a tannery.  Should they desire, tanneries could preserve surplus hides for over a year by packing them in more salt.  Tanning is both a physical and chemical process that preserves a hide and converts it into leather.  The removal of membranes and subcutaneous fat from the underside and the optional hair removal on the topside entail just one or two physical processes.  The chemical processes reorganize some organic molecules, while often coating or replacing others with outright inorganic substitutes.

The leather industry has an odorous history and one accompanied by pollution. Today there are three distinctive methods to use for tanning a hide: by the ancient vegetable process, modern chromium process or novel aldehyde process.

Tanning liquors

Historically either alkali or acidic solutions have been used in tanning.  A Native American Indian might have soaked a deer hide in a potash solution for example.  Also called “lye”, this caustic alkali or base solution of potassium carbonate can be created simply by leaching water through wood ashes.  Lye (potash/potassium carbonate, sodium hydroxide/caustic soda & potassium hydroxide) or other alkali solutions like hydrated lime will remove the hair from hides.  Both sodium sulphide and sodium hydrosulphide will dissolve hair.   Even some weaker alkaline solutions like ammonia collected from human urine; have the effect swelling the hide, enlarging follicles and loosening hair at the root.

* Several centuries ago in urban areas like 16^th century London, it was common practice for poor children to collect urine from private “chamber pots” and public “piss pots” to sell it for money.  Urine is a rich source of urea and decomposes into ammonia, which was an important source of nitrogen to factories that could not yet synthesize such a chemical independently.  At least three important industries required urine back then.  Textile manufacturers used ammonia for altering the color of vegetable dyes and adjusting pH in dye baths, gunpowder makers needed the nitrogen found in urine to make critical potassium nitrate and tanners also needed or favored urine to produce leather. 

* Even back in ancient Rome, urine pots were placed in the streets for the public to fill at leisure.  These pots were collected and used to wash laundry.  The laundry came out bright and clean and the practice was so popular that Emperor Vespasian taxed this urine in the 1^st century AD.

* Today household ammonia (5 – 10% pure ammonium hydroxide) is still critically acclaimed for its general cleansing ability, including for laundry.  Just don’t mix ammonia with bleach (calcium hypochlorite) because that will create dangerous fumes.   

Two mildly acidic and astringent chemicals used to produce leather are alum and tannin.   Alum (or specifically hydrated potassium aluminum sulfate) is used as a blood coagulant in articles like styptic pencils, in underarm deodorants, as a dye-fixer or mordant for wool and plant fibers and in tanning solutions where the hair or fur might want to be retained.  Alum creates a less toxic alternative tanning liquor and for small jobs is being used more frequently now than it ever was in the past.  Tannin is easier to find as it occurs naturally in the bark and leaves of several different plants. This astringent polyphenol binds to and coats collagen proteins, making them less water soluble and less vulnerable to bacterial decomposition.  Tannin is but one type of polyphenol out of thousands, and these phytochemicals give vegetables and fruit both their color and beneficial antioxidant properties.

* Astringents taste bitter to the tongue, pucker up the mouth and tend to shrink or constrict body tissues in general. An astringent tanning liquor then can be expected to tighten its hold upon hair, as opposed to a lye liquor that would swell and loosen its hold. 

* Tannin from tree bark is far more traditional than tanning liquor from alum. By the early 17^th century Industrial Revolution, large plots of the northern English countryside were being ravaged to mine alum rich shale deposits, which were then baked in bonfires using all the firewood from the surrounding landscape.  Probably more of that alum found its way into textiles than leather but by this time England was running out of trees too. 

In the past the commercial treatment of leather with tannin required massive amounts of tree bark (approximately an equivalent weight of bark to the weight of a skin).  In America, after the forest near early Boston and New York City were denuded, tannin harvesters ascended to the Catskill, Adirondack and Allegheny mountains to placate their ravenous need for tannin. Whole hemlock forests were flattened of trees, merely for the tannin in tree bark while the softwood was largely abandoned. The practicality of building tanneries closer to the source of tannin and then shipping hides long distance rather than tree bark was eventually realized.  Leather tanneries often formed the central economic hub of many new communities in American outward expansion.

The word “tannin” is derived from a German word meaning oak.  Several different plant species (including chestnut, eucalyptus, mangrove, maple, sumac, wattle, and willow trees or bushes) are high in astringent tannin and are commonly used in vegetable tanning liquors.  It would be possible to leach a tannin rich tea from the dead leaves of most any deciduous tree in the autumn.  Some people have boiled bran (the husk of wheat or rye kernels) to obtain tannin.   Hemlock tends to make leather reddish-brown while oak produces yellowish-brown and chestnut while famous for making thick Italian shoe-sole leather, turns collagen fibers dark brown.  Before introduction of chrome tanning solutions in 1858, most all leather produced was simply “vegetable tanned” leather.

Keith Weller acquired from USDA ARS

So around the same time that the trans-American railroads were being constructed, Texas cowboys were driving cattle herds up to meet the railhead and jobless Civil War veterans were harvesting wild buffalo for meat; new chromium leather tanning techniques were suddenly gaining favor in Europe.  The new rails were soon used to ship cattle back east (notably to Chicago) and products like buffalo hides back further east to established tanneries perhaps in Boston or New York City.  The fact was that those eastern American tanneries relied upon much human labor and slow vegetable tanning chemistry.  Typically a cow hide might need to soak in a barrel of tannin liquor for six months to produce high quality leather.  Although not especially desired or in demand by American tanneries, a few bundles of Buffalo hides made their way to England; where they were enthusiastically received and thousands more were immediately ordered.  The decimation of the great American Bison herds is directly traceable to bovine diseases spread from domestic cattle and the commercial slaughter demanded by global economics.  In a twelve year period beginning in 1871, about six million buffalo hides from approximately nine million animals slaughtered – were shipped to Europe.

for source and enlargment: https://commons.wikimedia.org/wiki/File:Bison_skull_pile-restored.jpg

Chrome

Somewhere back in the middle of the 19th century, the effects of Chromium (III) upon a rawhide were discovered.  These solutions came from dissolving elemental chromium in sulfuric or hydrochloric acid. Two solutions, chrome alum (or chromium (III) potassium sulfate) and chromium (III) sulfate are noteworthy in tanning.  The latter of the two solutions is the simpler, cheaper form preferred today by the commercial tanning industry.  Not nearly as toxic as the hexavalent chromium (IV) variety of chrome used on shiny automobile parts, chromium (III) tanning liquors nonetheless contain heavy metals and should be disposed of carefully.  In the right pH environment chromium (III) can oxidize into undesirable and environmentally persistent chromium (IV).   Chromic acid which is different but related, is noteworthy for being a strong and corrosive, oxidizing agent that will attempt to consume organic compounds.

About 85 percent of all leather today is chrome tanned.  ‘Chrome tanned leather’ is thinner, more eaten away and more flexible than ‘vegetable tanned’ leather.  Chrome tanned leather is good enough though for most situations and may even be the preferred choice in a few applications; given its flexibility and better resistance to shrinkage caused by water.  Some chromium remains behind in the hide after tanning, as it is tightly bound to the collagen proteins.  The reason that chromium has become so ubiquitous in today’s tanning industry is because it allows great reductions in both time and labor.   Vegetable tanned leather which is more expensive, is usually reserved for quality items like belts, purses, wallets, shoe soles, horse bridles, harnesses and saddles.

https://en.wikipedia.org/wiki/File:Igualada-Museu_de_la_Pell_(7).JPG

Both vegetable but especially chrome tanned hides are tumbled and pounded around in rotating drums like the museum piece imaged above.  Once the desired level of chrome penetration into the hide is achieved (which takes about 24 hours) the hides will come out “wet blue”; not the tan color shown.  Several varied finishing techniques would follow next.

Whereas vegetable tanning might require grueling labor for fleshing and stretching the hide and long months of exposure to tannins inside a vat, chromium tanning creates a product in just days or weeks.  The substantial chore of fleshing is much simplified by virtue of these chemicals dissolving most of those unwanted fatty tissues. The details of temperature, pH and other chemical factors are more complicated, critical and caustic with chrome than with vegetable tanning liquors.  In this present day and age, one can no longer just buy U.S.P. approved chromium potassium sulfate crystals from the local drugstore either.  Chrome tanning on an individual basis is not practical, but vegetable tanning is.

Aldehyde Tannage 

While chromium (III) solutions leave tumbled hides a color that is referred to as “wet blue” a newfangled process leave the hides “wet white”.  The first and most notable, quick working base chemical used in “chromium-free” aldehyde-tanning was the water soluble gas, formaldehyde.   Not creating the pollution that chrome does, some small amount of toxic formaldehyde residues nonetheless remain within the clothes, shoes and car seats made with this leather.  A newer chemical called glutaradehyde is highly reactive towards proteins, but leaves aldehyde wet white leather comparatively ‘baby safe’ and allergen free.  Glutaraldehyde is more expensive than formaldehyde, it sterilizes or inactivates viruses and bacteria, it is used to remove skin warts and is occasionally used in hydraulic “fracking” fluids to unclog oil wells of microorganism buildup.

The American Indians and probably many other nomadic aborigines as well typically used the brains of an animal during the hide tanning process.   Boiling the brains with a bit water creates an oily soup that can either be used as a solution to completely submerge and soak a hairless hide or be rubbed into the underside of a fur.  Once the treated skin is smoked over a fire however, chemical changes occur and a mild aldehyde type tannage takes place. Almost any organic oil benefits the flexibility and durability of leather.  Some famous leather ointments like Neatsfoot oil however will darken leather while brain oil is less likely to.

*Neatsfoot oil (a brand name) actually comes from the tibia (lower leg –shin bone) of a cow; it doesn’t easily freeze and absorbs readily into leather.  Sulfating the Neatsfoot oil allows it to penetrate even further. 

Price of rawhide

The U.S.A. is only the eighth largest producer of leather in the world, with a total 669 million square feet produced in 2011.  The other top ranking leather producers superseding the U.S. that year were: China (3,913 M sq. ft), Brazil (1,832 M sq. ft.), Italy (1,573 M sq. ft.), Russia (1,460 M sq. ft.), India (1,397 M sq. ft.), South Korea (1,083 M sq. ft.) and Argentina with 715 million square feet of leather produced.

In the 1990’s the price of a wet nondescript cowhide in the U.S.A. was approaching $1.00 per square foot. Today’s price for a wet steer hide (over 53lbs.) from a slaughterhouse is about $70.00.  Because of its potential as leather, raw cowhide is generally more valuable than pig, sheep or goat hide.  However if the hair is to be retained then hair quality or unusual coloration like Angora goat or Holstein cow can fetch much higher prices.  There are authorities on this subject.

The price of meat influences the price of leather.  Tanneries must compete with food companies to get the hides because what is not converted to leather is immediately converted to gelatin instead.  Gelatin is made by boiling the collagen from skins, tendons, ligaments and bones in water.  Europe produces a large share of the world’s gelatin, supplying about 400,000 tonnes per year.  More pig skin is converted to gelatin than is cow, sheep or goat skin.  Gelatin itself is used in puddings, candies, marshmallows, ice creams, cakes, shampoos and miscellaneous cosmetics.

Removing the hide

 Flaying or “skinning” the hide usually takes one or more very sharp and slender knives.  These knifes generally dull quickly while skinning and need to be re-sharpened periodically.  The thickest skin on an animal is usually around the neck and shoulders.  The thinnest skin, which is more vulnerable to nicks by a skinning knife, is at the belly.   When removing the skin in one piece the starting incision is usually made from the chin, down through the center line of the belly, to the rectum.  From each foot, cuts running down the inside of the legs come down to meet the centerline.

Small the animals have thinner skins than large animals.  The most difficult skinning would have been preformed by a fur trapper that was compelled by market demands to tediously flay around the head, face and feet, or by a taxidermist who’s flaying gets even more intricate.  Furriers and taxidermist are rare these days but their profession still requires much more skill, patience and attention to the details of skinning than an average hunter would employ.

“There is more than one way to skin a cat”

Large industrialized slaughterhouses can remove a full grown steer’s hide in less than a minute.  Techniques differ but these factories usually employ moving assembly line division of labor or small teams working simultaneously on one carcass.  Skinners might use  pneumatic “roller skinners” or normal knives and a mechanized skin pulling apparatus.

factory skinner using a flaying knife

team using a hide puller

For small furs like rabbit and mink a commercial furrier might purchase or construct a hide pulling machine that quickly shucks the skin, leaving it inside out.  The only labor involved is making a few precise cuts beforehand, around the head and feet.

DIY Vegetable Leather Tanning

There are many, many books, pamphlets, magazine articles and YouTube videos detailing “do-it-yourself” tanning techniques.  The novice should focus on the overall intent of tanning and less upon one particular technique.  The intent is always to remove the natural water and fatty tissues from a skin and replace them with something else.  A novice should initially avoid tanning large hides and seek something smaller. The amount of labor required for a large hide (bigger than a deer or sheep) can quickly become discouraging or overwhelming for the un-initiated.  The first decision to be made is whether or not the hair should be removed.

Caustic lye, potash or lime would be normal choices for de-hairing solutions.  It is possible however to simply submerge and tie a deer hide perhaps in a cold mountain stream and leave it there for a week or two. Returning later one will find that the hair pulls out easily by hand, no caustic solution was needed.  Many sources are adamant that the first thing to do with a hide is to scrape the flesh from the underside.  Alternatively though other tanners might prefer soak a hide first, thereby loosening both hair from one side of the hide and softening those fatty flesh tissues from the other.  If the tanner of furrier decides to keep the hair then he skips the de-haring alkali bath and moves on to fleshing.

* Buffalo hunters in the past didn’t flesh their hides at all, but cured and preserved the hides for shipment by spreading on salt and drying them out in the sun.

The “Indians” native to North America were expert leather tanners.  Every bit of their clothing was made of leather and often their homes were as well.  For scraping the hide they used tools made of bone, rock, wood or antler.

Factories involved in vegetable tanning were also compelled to physically flesh the hide and they historically favored a fleshing knife and a beam.  The fleshing knife is simply a rather dull, flat strip of metal with two handles.  The beam was usually a short log angled from the workers waist, to the floor.  This provided a work surface that allowed the wet and heavy hide to be moved around easily, and provided a mechanical advantage by allowing the tanner to lean into the work with his weight.

Once properly fleshed, either a de-haired hide or a fur with all its hair intact will undergo essentially the same processes afterwards.  While tannin will stain things brown it may be desirable for de-haired hides but an alum solution might be chosen for hairy furs.  Small animal furs might need to soak in a tanning liquor for just a few days whereas large hides might need to soak for weeks.   The judgment call of whether a hide has set in a particular tanning liquor long enough or not, is made by cutting through a small piece of hide and examining it in cross section.  If the sample cross section is the same consistent color throughout then this part of the procedure is finished.  The hide is now tanned from a chemical perspective but much physical labor remains.  Any pinkish-ness or fluctuation in color from the edge to the center is an indication to soak the skin some more.

At this point, should the treated wet hide or fur be simply tossed out upon the ground to dry, it would shrink, curl and stiffen into a very unusable product.  To get the strong but flexible leather we are familiar with that hide needs to be washed, rinsed, twisted or rung out like a towel and then thoroughly tortured as it dries.  A half dried skin can be laid over a tree stump and using a soft mallet, pounded over every square inch of its surface with short glancing blows .  At some point before all the moisture is gone, the leather is oiled.  It is this tedious but important, continual stretching, pounding and working of the skin as it dries, that produces flexible leather.

   Un-tanned rawhide can be preserved by drying it out.  If it is not to be tasked with some immediate purpose like being stretched over a hollowed out log to make a drum, then it can be saved for proper tanning at a later date.  Some rawhide might exist in a transition state, being only partially tanned.  Stretching a hide on a frame, or tacking one to a barn wall are popular methods of drying skins out.  Residual bits of fat or flesh can be scraped at leisure, either the suede or epidermis side can be attended to and once it’s flat & stiff the dried rawhide can be stored inside.

The novice or independent furrier has many options to improve his fur.   Furs can be washed in dish-washing detergent to remove oils and odor.  Vinegar and salt solution can be used to “pickle” the skin which helps “set” or lock in the hair.  The pickling solution is usually neutralized with baking soda before the fur hits the alum bath.  Once dry after the tanning bath, a fur might be rinsed in gasoline or naphtha (white gas used in camp stoves and lanterns) to remove any lingering oils or odor.  [Dry cleaners predominately used naphtha or another flammable petroleum fraction before 1911].  The flesh side of the fur might be sanded with sandpaper to remove high spots, making the suede uniform and level.  When finishing a fur it might be brightened by tumbling it in cornmeal, bran or sawdust which is then combed or brushed away.

Individual tanners working with a hairless hide might consider smoking it over a fire.  Some American Indian tribes once made the majority of their clothing from smoked deer hides.  After being fleshed, de-haired, cured in a bath of boiled tree bark tannin, worked to pliability and bathed in fat or brain oils, a deer hide was commonly draped over fire.  Being supported by a little tent like frame of green tree boughs the hide was rotated occasionally, collecting preservative chemicals and additional color along the way.

Once again, there are many sources and even videos of this topic available in the library or on the Internet.  Some of these sources have excellent information others do not.  The reader should be aware of several alternative vegetable tanning methods or recipes before religiously adhering to just one.

Other leather

   There are some schools that teach tanning and/or taxidermy and colleges or universities that offer chrome and aldehyde tanning curriculum.  There are products that disguise the origin of leather and some new organic products for vegans that imitate leather.  Often commercial leather is split, yielding at the least two different products; a “top grain” and one or more layers referred to as “split hide”.

Patent leather has a shiny, glossy finish and gets its name from a finishing and polishing process that was patented some two hundred years ago.  A satisfactory substitution or duplication of that process can be created by painting leather with layers of pigmented linseed oil (similar to oil painting on a sheet of canvas) and then with layers of varnish or lacquer.  Modern patent leathers (not vinyl or poromeric imitation leathers) usually have plastic coatings.

An “aniline dyed” leather refers to a very high quality ‘top grain’ leather that has been dyed clear through with a soluble dye.  A hide’s entire natural surface with pores and imperfections is visible with aniline dyed leather. No sealer, paint or insoluble dyes were used.  Should imperfections like scratches, blemishes or scars be sanded or disguised then the improved leather is referred to as “semi-aniline” dyed.  Most leather car upholstery is “pigmented” leather, meaning“semi-aniline” dyed leather with a heavy durable, protective, pigmented polymer surface coating.   Aniline is also a precursor used in the manufacture of polyurethane.

The Chinese were known to have boiled leather to make armor.  Probably many cultures over the centuries used leather armor but few if any examples exist in the historical record because they would simply biodegrade.   There might have been a lot of boiled leather armor back in medieval times but no one knows for sure now.  Boiling leather makes it shrink, thicken and harden.  Boiled in water or perhaps oil or tallow, the leather becomes mold-able for a short time and will freeze or set into shape as it dries. Overcooking makes it brittle and likely to shatter.  This site discusses making leather armor.

Authentic cheetah, giraffe, tiger and zebra hides are rare now but they were once fairly common.  Some leather producing outfits have taken to printing the hair of cow hides with ink, in patterns resembling these animals.   Even the hides of Holstein cows might be suspect.

As long as people continue to eat meat, there will be a continual supply of animal skins.  The rate of human population expansion is unsustainable and as a species we are soon to eat ourselves off this planet.  Nonetheless some vegans and or members of PETA (People for the Ethical Treatment of Animals) would have us believe that many animals are raised and slaughtered solely for the leather.  Aiming squarely for this demographic, companies like MuSkin, Myx and Mycoworks are actually growing, convincing leather substitutes by using mushrooms.   A substrate, matrix or mat of linen or hemp fibers actually gives this artificial leather its integrity and strength.  In essence either the chitin from the cap or the mushroom mycelium itself fills the spaces between mat fibers.   Apparently incubation and manipulation of fungus while growing can be controlled to a point where zippers can be incorporated without sewing.   Apparently members from the gilled Pleurotus genus and the non gilled Phellinus genus of woody mushrooms are producing the best mushroom leather  <images> or <other images>  results.

MISC informative LINKS

Some chemicals used in leather processing

Phenol

Hemlock history in New York

Buffalo destruction / global market

Ethnobotany of tannins

Leather furniture facts

World Statistical Compendium for raw hides and skins, leather and leather footwear 1993-2012   <PDF>

 

 

Hot Stuff 3 – Rocket stoves to meat smoking

Pertinent

Versions of the “rocket stove” principle have been manufactured for about 90 years, so the concept must be older.  Above is a cheap and quick example of a rocket stove made with about seven tin cans.  The barrier between the inside chimney of small cans and the outside layer of large ones, is insulated with sifted wood ashes.  Rocket stoves are efficient for cooking because they burn hot and use very little fuel.  The “rocket” name undoubtedly stems from the vigorous manner in which air, flame and smoke are all drawn into the chimney.

For free standing little cook stoves and water heaters the optimum chimney height might be a little less than three times whatever inside diameter is actually chosen for the chimney.   These proportions seem to engender the best draft.

Once a fire has been ignited it takes a few minutes for the stove to become normalized.  Once hot and working correctly these little stoves consume almost all the volatiles in smoke and leave little pollution.   Using just dry twigs these stoves are capable of reaching 1,600 – 1,700°F (926°C).    * That’s a temp high enough to melt tin, lead, zinc, antimony, magnesium, aluminum and lava – but not silver, gold or copper.

Iron stoves or the ‘tinplate’ steel found in a soup can will not stand up to long term heat of this degree because of the accelerated rate of oxidization.   For this reason a stainless steel, ceramic or refractory version would be desirable for stove longevity.

Slick stoves working upon the rocket principle have been made with cinder blocks and stacked bricks.  This link is to a rocket stove manufactured in China.  These are practical products but seem a bit costly.

A long lasting cementatious rocket stove can easily be made at home.   This image (idea robbed from a video) depicts creating a mold from plastic sewer pie and a 5 gallon plastic bucket.   Yes the mold could be filled with plain cement but a refractory mix would be more desirable.   A concrete rocket stove would conduct heat and become hot to the touch and would also be heavy to move.   A stove cast of proper refractory would be lighter weight and insulated, allowing desirable higher heat inside the chimney.

Opinions and examples of refractory mixes vary widely.   Perlite and vermiculite are frequently listed as light weight insulating ingredients in refractory mixes.  If the intended function is not too demanding, wood sawdust or peat moss might substitute as the light weight, insulating ingredient.  Perlite is a volcanic glass that has been ‘puffed up’ like popcorn (with the help of escaping steam when it was created).   You’ll frequently find little individual white beads of perlite mixed in with commercial potting soils, or sold in bulk at plant nurseries as a soil amendment.  Exfoliated vermiculite possesses many of the same qualities as perlite.   Fireclay is an ingredient used in the refractory of brick, ceramic and glass kilns, because few other building materials can repeatedly withstand such high working temperatures.   An easy to remember recipe for an adequate refractory mixture would be four equal parts each of sand, Portland cement, fireclay and perlite (or vermiculite).  Those proportions could be tweaked a bit to reduce sand and cement (1.5 sand, 1.5 cement, 2 fireclay, 2 perlite).

When casting a mixture like this it is important to use as little water as feasible to ensure the strength of the concrete (refractory).  Do not forget to allow adequate space at the bottom for insulation of the chimney and remember to tamp this first, with a stick, before filling the remainder of the mold.   A wire skeleton or armature of some sort would greatly enhance the long term resilience of such a cast.

Two centuries or more ago, the chimney in the center principle was being exploited by expensive handmade self heating teapots known as samovars.   Manufactured portable utensils for heating or sanitizing water outdoors began to be seen in numbers for the first time however during WWII, when the New Zealand Army issued their soldiers with mess kits containing jacketed kettles.   ‘Storm kettles’ or ‘volcano kettles’ work well in windy or rainy weather.  Fuel from twigs to straw to buffalo chips can be found almost anywhere and cost nothing.

Not commonly found in American sporting goods stores, these kettles are made by several little companies and are produced in either aluminum or stainless steel versions.   Rather than pack into the woods a stove that requires special fuel (sterno, denatured alcohol, hexamine tablets, paraffin wax, kerosene or  naphtha (white gas)) it seems more logical to carry one that simply uses fuel which can be picked up from the ground.

Thermette:  Ghillie-kettle:  Eydonkettle:  Kellykettle

——-

For some time now some people have been using a larger form of the rocket stove, known as a “mass heater”, to warm the home.  In this case the exhaust from the chimney is captured and turned downward, then circulated through a wall, the floor or a banco (bench).   The masonry in the wall, floor or bench acts as a thermal mass or heat sink that collects the heat and releases it slowly.  So from the illustration above an oil drum or other metal hood accomplishes the first heat exchange to the room’s atmosphere.  Any remaining heat is ideally captured by a thermal mass before the exhaust is finally released to the outdoors.

A few examples of these thermal mass heaters are found almost all over the world.  It would be very feasible to pre-heat water for the home by wrapping a water line around a rocket stove’s chimney.   Potential construction concerns for building a mass heater of this type include ensuring that the draw of the stove is sufficient to push exhaust through a long ductwork.  One critical dimension is the distance between the top of the chimney and the hood (drum).   Some people brag that the amount of firewood needed to warm their house was reduced by 75% after resorting to a ‘mass heater’.   One should consider however the extra time spent splitting wood into pieces small enough to feed into this stove, and the extra attention probably required to keep the (fast burning) stove continually fed.   Depending on size it may take several hours to several days to equalize the thermal mass, so hopefully in the meantime the house would be equipped with an auxiliary source of heat.

 

Added 7/27/2016

The rocket stove mass heater takes its idea from the much older masonry stoves and or ceramic stoves of Europe and Russia.  Usually constructed of brick and covered in tile these often massive heating appliances are at least one thousand years old in design principle yet are still “greener” and more efficient than modern heating alternatives. 

http://commons.wikimedia.org/wiki/File:Schloss_Hohenaschau_Gotische_Stube_2.JPG

The typical “tulikivi” (Finnish), “kachelöfen” (German), “kakelugn” (Swedish) or “pechka” (Russian) oven stoves only need to be fired about twice a day to provide a continuous 24 hour heat.  In some homes the people sleep on them, or may also bake with them.   When designed well they burn very hot and therefore leave little creosote buildup behind.   Inside the fire’s exhaust must furl around a labyrinth of baffles before it can escape, providing time and surface area for energy transfer.

In the last century or so of newer building construction, massive masonry heaters like these were usually replaced with much smaller coal, oil or natural gas burning alternatives.   

http://evan.fmschmitt.com/francis/Depression-history.html

The cast iron wood cookstove became a favored house heating appliance in America homes between the 1870s and the 1920s.  They were advertised in newspapers and mail order catalogues and were manufactured by a host of different companies like ACME, Acorn, Garland, Majestic, Monarch, Peninsular, Pilgrim and Sterling.  These wood stoves or ranges could act as energy centers perhaps for the whole house and they supposedly baked a better loaf of bread than any modern gas or electrical counterpart.   Different models came with different options including ornate chrome (probably nickel) trim, hot water reservoirs, foot latch, thermometers, broiler drawers and secondary warming chambers.   Cooking on such a stove could require much patience to establish the fire, because in addition to the firebox some models came with an adjustable main draft regulator, check draft regulator, stove pipe damper and an auxiliary damper.  It was standard practice for a housewife to keep a stock pot on the back of the stove, where she put leftover scraps of meat and bone.   Comfortable and desirable in the winter – these stoves could become beast to cook with however on hot summer days. 

 

 Pertinent links-

Tile stoves

Masonry heaters

New wood stove

———————————————————-

After reconsideration the project on the right above will be redesigned from an “L” shape to a “J” shape, to allow fuel to be fed from the vertical axis.   Sheet metal screws will be reversed so that they can be removed from the inside.  After that cans are to be wrapped in plastic food wrap and a chicken wire armature will be wrapped around the cans – suspended about an inch away.   After that a refractory mix will be slathered over the armature to a depth of about 2 inches.    Some of the metal cans will be too hard to remove initially, until years afterwards when the rust can then be pulled from the refractory easily.

(Slideshow below added August 2016)

This slideshow requires JavaScript.

 

 

The image above is a little incongruous with the topic of rocket stoves, but since it is related to fire and cooking and was available, it is included now.  Methods for cold meat smoking are diverse and numerous.  This image depicts a homemade variation of a commercial product which blows a steady stream of wood smoke into a meat holding chamber.   The main feature is the venturi which in this case is powered by a tiny air pump (like one used to aerate a fish aquarium).  The can below the homemade copper venturi needs a lid that will open and close; to insert wood chips or remove ashes.  The can needs some holes in its bottom so that combustion air can be drawn up through the smoldering woodchips.  Twelve to sixteen ounces of (hardwood) wood chips should provide about three hours of smoke.

There is not enough time and space left in this installment to adequately explain the important details of meat curing.   Remember that the wealthier half of civilization has only possessed artificial refrigeration for the last century or less.   Salt and smoke dehydrate -bloody raw meat.  Salt and smoke and cold weather have historically been the preferred tools for preserving meat by protecting it from bacterial spoilage.  Traditionally, smokehouses worked continually around the clock and pretty much throughout the year.  It is recognized by some that today’s commercial hams and bacons will putrefy long before they should (had they been properly cured and smoked by traditional methods rather than by quick methods).

In 1832 it was discovered that pyroligneous acid from creosote in wood smoke was the antiseptic preservative which protected meat.  Today commercial meat processors commonly inject into boned meat, salt, nitrites, nitrates and sulfides.  Before slaughter the animal may have been fed antibiotics, steroids or additives like ractopamine hydrochlorid.  About 70% of all chicken and beef sold in the U.S. and Canada is actually treated with carbon monoxide before you buy it.   The best way to tenderize meat without resorting to chemicals, is to cook it slowly.  Nowadays the best reason for treating meat to wood smoke (longer is better) is for the taste.

Familiar Batteries

 

Although at first they may appear to be mundane topics for discussion, batteries are contributing in ever increasingly important ways to the modern lifestyle.   Items from spacecraft to even some failing human hearts depend upon batteries.    Although a myriad of battery types and chemistries exist, none are ideal or are very long lasting.   In almost every category the quest for a better battery solution, is an urgent one.   Here in this post an attempt is made to illuminate the construction, advantages or limitations, recycle-ability and where applicable the proper recharging of some of the most common consumer grade batteries.

The “dry cell” battery made its first appearance during the Paris 1900 World’s Fair.    From this evolved the zinc-carbon cells which were so ubiquitous during the 1960’s.   Such cells are not dry, but actually contain an electrolyte of moist paste.   So-called “heavy duty” (zinc-chlorine) cells began to appear which offered an improvement in performance by featuring purer chemicals and an electrolyte of zinc chloride.   In today’s marketplace zinc-carbon and zinc-chloride cells have been largely displaced by the more expensive alkaline cell.   So far, all of these cell types are progressive variations of the original Leclancé cell invented around 1866.  In some circles zinc-carbon cells are simply referred to as Leclancé cells.

Leclancé cell image modified from public domain source

The term “primary cell” denotes a battery which is intended to be thrown away and not recharged after use, while the term “secondary cell” denotes a rechargeable type.   Battery chargers for zinc-carbon and zinc-chloride batteries have been built in the past but their effectiveness was minimal and the process fairly pointless.  The components of these old style cells contain materials however which might be useful to an experimenter.   For example the cases of Leclancé type primary cells are made of useful zinc.  The carbon graphite rod at the cell’s center can be filed to a point at one end and when attached to a 12v automotive battery, can be used to expeditiously solder electrical connections in an emergency.

Furthermore both zinc-carbon and alkaline cells contain manganese oxide (specifically manganese (IV) oxide) ; a common inorganic pigment used in dyes, paints, ceramics and in glassmaking.   As long as 19,000 years ago in Europe prehistoric cavemen were painting cave walls black and dark brown with manganese oxide and were achieving umber, sienna & burnt sienna hues by mixing or cooking in with this, varying amounts of iron oxide.    Ammonium chloride (NH4Cl) composing the electrolyte of the zinc-carbon cell is made by the reaction of hydrochloric acid and ammonia.  This chemical has a wide range of applications.   Also known as Sal ammoniac, ammonium chloride can be found in food additives, baked bread where it acted as a yeast nutrient, salty licorice candy, cattle feed and in some cough medicines where it acts as an expectorant.   Ammonium chloride acts as a nitrogen source in some fertilizers, it can be found in the glue that bonds plywood and as a thickening agent in certain hair shampoos.   Ammonium chloride can clean a soldering iron.   It is used in some soldering fluxes and once upon a time in the past it was even used (along with the help of a little copper) to produce green and blue colors in fireworks.   Zinc chloride (in Heavy Duty cells) can also be found in non electrical, corrosive soldering fluxes.  Sometimes used as a disinfectant, in antiseptic mouthwashes and dental fillings, zinc chloride of higher concentrations can also dissolve cellulose, starch and silk.  Zinc chloride is also a frequent ingredient in military smoke grenades.

In a battery, energy density is the amount of energy stored in a given space per unit volume or mass.  Alkaline battery cells have 3-4 times the energy density and a much improved shelf life compared to a zinc-carbon cell.  Appearing on the market in the late 1960’s, these usually have an outer shell made of steel.  Although generally thought of as primary batteries and contrary to what might be stated on a label, alkaline cells can be recharged.  A small current at about 65mA, interrupted periodically will do the trick.  Commercial pulse chargers for alkaline cells are available but rare.   Alkaline cells get their name from the strong base of potassium hydroxide (caustic potash) used in the electrolyte.   Potassium hydroxide (KOH) is hygroscopic (with a high affinity for water) and is sometimes used as a desiccant.   Some shaving creams, cuticle removers and leather tanning solutions to remove hair from animal hides – employ potassium hydroxide.

File source: http://commons.wikimedia.org/wiki/File:9V_innards_3_different_cells.jpg

The 9 volt battery is properly termed a ‘battery’ because it is composed of a bank of individual 1.5 volt cells.  The construction of the 9 volt battery has varied over the years but nowadays the most common assembly is of 6, rarely seen AAAA type cells.

Some other less common primary dry cells that won’t be discussed here include: the aluminum battery, chromic acid cell, nickel oxyhydroxide battery, silver-oxide battery, and zinc air batteries.  Again, the main difference between a primary battery and a secondary battery is the ease with which the chemical reaction within the cell can be reversed.   “A battery charger functions by passing a current through the cell in a direction opposite to that of the flow of electricity during discharge.”

It may be useful at this point to realize that the spiral wound (Jelly-roll or Swiss-roll) construction of some of the next battery cells to be mentioned and the construction of some capacitors can appear to be similar.  Over time in spiral wound batteries and capacitors alike, crystalline structure in the plate material or electrolyte eventually changes and causes complications.   Also the separators that isolate plates can deteriorate with age, eventually allowing opposing plates to make contact and short out.  When old devices like radios, stereos and TV’s stop working it is often discovered that bad capacitors caused the problem.   Simpler than a battery cell, a capacitor doesn’t produce electrons – it only stores them.  A capacitor can dump its entire charge in a split second whereas a battery cell discharges much more slowly.

Nickel–cadmium batteries (NiCd or NiCad) got their name from the chemical symbols of their electrodes.   The first NiCD battery was a wet cell created in Sweden around 1899.   Beneficial attributes of this type of rechargeable battery include its tolerance to being deeply discharged for long periods, the fact that it can withstand very high discharge rates with virtually no loss of capacity, its lower self-discharge rate, and its performance in cold weather.  Outdoor solar patio lamps are one application where NiCds work admirably.   Negative attributes of the NiCd type would include a phenomenon known as voltage depression (voltage depletion, “lazy battery” or “memory” effect).   Voltage depression in this case is attributable to increased internal resistance caused by metallic crystal growth in the cadmium.   Improper or unsophisticated recharging of NiCads is probably the main reason for the continuing decline of their popularity.  The surface of the cadmium plate in a good NiCD cell has a small crystalline structure.  When these crystals begin to grow then the surface area is reduced so voltage depression and loss of capacity result.  The crystals can grow large enough and sharp enough to penetrate the separator between electrodes.

* It is sometimes possible to temporarily reclaim “spent” NiCD cells or battery packs with a trick.  By zapping NiCd cells or battery packs with a strong DC current like that from a welder or automotive battery charger (where positive to positive and negative to negative terminals meet) the size and sharpness of the crystalline dendrites within the cadmium hydroxide electrode can be reduced and performance partially restored.   Even battery packs that seem to have been dead for several years can be recovered this way.  If not used constantly however these seem to return to their original dormant state much sooner than they should.  Nickel based cells have venting mechanisms to allow gasses to escape in the event of heat from overcharging.  Therefore the electrolyte might dry up.  As with other “dry cells” the electrolyte can migrate away from the terminals over time also.

There is not much that can be reclaimed from either a NiCd or NiMH cell.   Cadmium hydroxide is more basic than zinc hydroxide.   Cadmium (Cd / atomic # 48) is a rare, soft, ductile and toxic transition metal that is found in trace amounts in most zinc ores and is often collected as a byproduct of zinc production.  Sometimes replacing zinc for corrosion resistant coatings, cadmium electroplating of steel is common with aircraft parts.  Cadmium can be found in nuclear reactors where it controls neutrons in nuclear fission.   Red, orange and yellow paint and plastic pigments are often made with cadmium.

NiMH cells (Nickel-Metal Hydride) are similar to NiCd cells, having replaced the negative cadmium electrode with one of a hydrogen absorbing alloy.   Superior in some ways but not in others to NiCads, NiMH cells only arrived in the marketplace in 1989.   Having 2-3 times the capacity of a NiCd cell they are useful in high drain applications like the demands from digital cameras as an example.   NiMH cells however have a very high self-discharge rate (perhaps 30% a month).  That means that they lose their charge just by doing nothing.   NiMH cells exhibit much less apparent voltage depression or recharge “memory” than NiCd types but it can still occur.  Unlike NiCd cells, NiMH cells should not be deeply discharged (except upon occasion before recharging) and they should be kept “toped up” or recharged frequently.

 * The amount of energy expended by a typical “AA” alkaline battery is about 5,000 C (Coulombs -> 1C = about 6,241,000,000,000,000,000 electrons).  Rechargeable “AA’s” and some alkalines display the relative capacitance of a cell with a “mAh” (Milliamp hour) rating.  One mAh = 3.6 C and 1,000 mAh’s = 1 Amp hour = 3,600 C.  Often compared to the gas tank of a car, the voltage represents how much gas is being used while the mAh represents the size of the gas tank.  A car with a bigger gas tank will go farther but the bigger gas tank will also take longer to refill.    

*  The mAh rating stamped on an “AA” battery can be misleading if comparing different types of batteries.  New alkaline “AA’s” might have a 2,500 mAh rating, while rechargeable  NiCd’s or NiMH’s might only be rated at 1,200, 1,900, etc.  In high-drain applications (like digital cameras) however these rechargeable cells will far outlast the alkaline types even before being in need of a recharge.  Alkaline batteries are not designed for high discharge demands, and only deliver full capacity if the power is used slowly.    

* Some of the first “button” type battery cells were mercury or mercuric oxide batteries.  Used in hearing aids, watches, calculators and other small portable electronic devices mercury cells were popular and common between 1942 and the early 1990’s.  In the 1990’s the European Union and the United States began to legislate this type of chemistry out of existence.  Mercury cells had a 1.35 nominal voltage and high capacity, achieved from using an alkali electrolyte with zinc and mercuric oxide electrodes.

File source: http://commons.wikimedia.org/wiki/File:Lipolybattery.jpg

Cells in the Lithium battery family use lithium metal or lithium compounds in the anode but vary widely in choice of cathode and electrolyte.  Lithium cells offer higher voltage and larger energy density than most other battery types but they are also far more expensive.    Depending on its chemistry a lithium cell can provide 3.3 – 3.7v of nominal cell voltage (compared to: 1.5v for zinc carbon, zinc chloride and alkaline cells, or 1.2v for NiCd and NiMH cells).

Lithium Prismatic cells of monopolar or stacked configuration are similar to the voltaic pile in concept – with the positive and negative plates are sandwiched together in layers with separators between them.   A new way to construct multiple electrode cells is to arrange them in what is called a “bipolar configuration”.   This looks like a stacked sandwich or prismatic configuration but here the negative plate of one cell becomes the positive plate of the next cell.   Almost a play upon words is the term “bipolar” because of the historic use of this unusual metal in treating manic depression (more commonly referred to today as “bipolar disorder”).   More on this bipolar topic momentarily.

Because they are pressurized and may use a flammable electrolyte “Lithium-ion” batteries can be dangerous.   A standard lithium cell is not rechargeable but a lithium-ion cell is.  While lithium primary cells have electrodes (generally anodes) of metallic lithium, rechargeable lithium-ion battery (LIB or Li-ion battery) cells use electrodes composed of various materials impregnated with lithium ions.   [Some examples are: lithium iron phosphate (LFP), lithium cobalt oxide (LiCoO2), lithium nickel manganese cobalt oxide (NMC)and lithium manganese oxide (LMO)].   Some of the newest battery designs being contemplated by researchers are impregnating carbon nanotube cathodes with lithium on a nanoscopic scale (particles usually measuring between 1 and 100 nanometers).  In the near future we may witness the commercialization of the so-called “nanobattery”.

The capacity of Li-ion type rechargeable batteries will diminish substantially after a few years.   Li-ion cells don’t have a “memory” and don’t get confused by shallow discharges.   It is not wise to strain such a battery by frequently discharging it completely, nor is it beneficial to keep it fully charged all the time.   Quick discharges also place strain on this battery type.  Over time a regularly used Li-ion battery will suffer less capacity loss than one that is used infrequently.   These cells don’t like extreme cold but they hate hot temperatures.

Popular lithium-ion polymer batteries (LiPo, LIP) should connote cells built with a non liquid polymer electrolyte that does not leak.   Confusing the issue however, manufacturers soon expanded this meaning to include lithium cells with pouch type flexible polymer casings.

* Lithium is a very curious material.  It does not occur naturally in a pure state because it is a highly reactive alkali metal with one of the highest reduction potentials of any element.  With an atomic number of only 3, refined lithium metal would be so soft in could be cut with a knife and so light that it would float on water.  A comparatively rare element and strategically important material, it is hard to acquire and therefore costly.   The price of the metal has sky-rocked since WWII.  During that war lithium was mainly used as Hi-temp grease for aircraft engines.  Soon later it was used to stage man’s 1st nuclear fusion reaction (1952 / lithium transmutation to tritium).  In 1954 when mixed with hydrogen (as lithium deuteride) it composed the fuel of the Bikini Atoll (Marshal Islands / Castle Bravo) thermonuclear “H” bomb.  This particular test surprised its designers by being a far more powerful blast than expected (@ 15MT the greatest yield of any U.S. nuclear test) and also created international repercussions concerning atmospheric thermonuclear testing.  Low concentration but stable lithium hydroxide was stockpiled for many years due to its strategic value in the manufacture of hydrogen bombs.  In nuclear power plants or ship/submarine reactors lithium might be employed as a coolant by moderating boric acid in the absorption of neutrons.   In some underwater torpedoes a block of lithium might be sprayed with sulfur hexafluoride to produce the steam which cranks the propeller.  Lithium is used in heat-resistant glass and the manufacture of telescope lenses because lithium fluoride crystals have a very low refractive index.  Chosen for their resonance, lithium niobate crystals are used in mobile phones.  Lithium is used as an oxidant in red flares & red fireworks, as a flux for welding and soldering and as a fusing flux for enamels and ceramic glazes because it lowers their melting points. 

https://en.wikipedia.org/wiki/File:CR2032_disassembled.jpg

Sodium affects excitation or mania in the human brain so doctors and psychiatrist might often issue lithium as a mood stabilizer.  For treatment of bipolar disorder / manic depressive disorder, lithium affects the flow of sodium through nerve and muscle cells in the body.   The terms for this disorder denote uncontrolled mood swings from up to down or high to low and back.   Lithium treats the aggressive, hyperactive and manic symptoms of the disorder.   In humans amphetamines produce effects similar to the symptoms of mania and herein lay another interesting quality of lithium.   Apparently lithium battery cells (a cheap source of the metal) are frequently used as a reducing agent in the illicit manufacture of methamphetamine.  One recipe called the “Nazi method” requires anhydrous ammonia, ether, lithium and pseudoephedrine.  A more complicated recipe also uses lithium but substitutes anhydrous ammonia with ammonium nitrate, lye, salt and a caustic drain opener composed of sulfuric acid and a cationic acid inhibitor.  Double methylated phenylethylamine (Meth) and its precursor amphetamine are both built upon the plant derived alkaloids ephedrine and pseudoephedrine.   Ephedrine and pseudoephedrine (from the Ephedra distachya plant) are active ingredients found in several brands of effective antihistamine.

The largest producers of lithium are Chile and Argentina.  Large deposits of lithium have been discovered on the Bolivian side of the Andes and there is a lot of the metal dissolved in the oceans.  Acquired primarily from brine lakes, clays and salt pans where it is refined electrolytically, production of the metal is slow.  There is no standard spot price for the metal in a futures market or stock exchange.  China has become the world’s largest producer and consumer of lithium ion batteries.   Presently ever-growing in utility and popularity and expecting huge requirements of this metal in future electrical automobiles, market analysts predict that production of lithium will soon fall short of fulfilling its demand.

The construction of lead-acid automobile batteries has changed very little in the last 50-60 years.   A standard car battery has a conventional voltage of 12.6 volts achieved with only 6 cells, because the nominal voltage of each cell is 2.1 volts.   Typically in each cell alternating plates of different polarity {+ containing lead dioxide (PbO2) and (-) of plain lead (Pb)} are separated by nonconductive paper or synthetic dividers and surrounded by an electrolyte of about 35% sulfuric acid (H2SO4) and 65% water.  The electrolyte of a healthy cell should have a specific gravity of 1.265 @ 80°F.

*   During the discharge cycle of a lead-acid battery; the negative plates (lead) combine with the SO4 (of the sulfuric acid- H2SO4) to produce lead sulfate (PbSO4) and the electrolyte’s specific gravity goes down.   The electrolyte becomes weaker and the potential between ± plates diminishes.   Conversely, during the charge cycle electricity is passed through the plates forcing SO4 back into the electrolyte.   The lead sulfate is broken up as lead oxide and plain lead are re-deposited upon their respective plates.   The specific gravity and voltage (potential between plates) are re-elevated to the proper levels.

Industry nomenclature- lead acid batteries

Aside from common automotive batteries, buyers also have access to “maintenance free” batteries, “deep cycle” batteries, “hybrid” or “marine” batteries, “gelled” deep cycle batteries and “AGM”(Absorbed Glass Mat) batteries.   The chemistry of these differing lead-acid batteries remains the same but the quality or quantity of the components change.  “Maintenance free” batteries are usually just heavy duty versions of the same basic design.   Generally the construction is better, components are thicker and the materials are more durable.   Commonly the plate grids contain cadmium, strontium or calcium to help reduce water loss by reducing gas.   Such batteries are often closed systems (can’t add water or check specific gravity) and they are often referred to as “lead-calcium” batteries.

Automotive batteries are optimized to start car engines.  The hardest work they are expected to do is to start a cold engine on a cold day.  Hence they are constructed internally with many thin plates within each cell, to maximize surface area and therefore current output.  An automotive battery is designed to produce a large current for a short time.  Unless abused, a car battery is seldom drained to less than 20% of its total capacity.  Allowing this type of battery to drain beyond that point (or allowing it to self-discharge by not using it for long periods) can be very detrimental to the battery’s longevity.   By contrast “deep cycle” batteries as used in golf carts, electric fork-lifts and for boat trolling motors are optimized to provide a steady amount of current for a protracted period of time.  These can be deeply discharged (80% of capacity –although doing so strains the battery), repeatedly whereas an automotive battery cannot be.   Deep cycle batteries have fewer plates but thicker ones within each galvanic cell.  The plates have higher density plate material.  Less electrolyte and better separators are also used.  Alloys used for the deep cycle cell plates may incorporate more antimony than car batteries do.

* Lead acid batteries generally have two common ratings stamped upon them; CCA & RC.   Cold Cranking Amps (CCA) is the number of amps a battery can produce –for 30 seconds @ freezing temperature (32°F or 0°C).    Reserve Capacity (RC) is the number of minutes that a battery can deliver 25 amps at or above a 10.5 volt threshold.

Generally, a deep cycle battery will possess only one half to three quarters the cold cranking amps but twice to three times the reserve capacity that an automobile battery will contain.  A deep cycle battery can endure several hundred total (complete) discharge/recharge cycles whereas a car battery is simply not designed to be totally discharged.  This reserve capacity and discharge tolerance makes deep cycle batteries preferable to automotive types for the purpose of off-grid electrical storage purposes.  Any lead acid battery however will last longer if it is not allowed to discharge to a great degree.  A battery discharged to 50% every day will last about twice as long as one cycled to 80% of capacity daily.  For less strain and increased longevity, deep cycle batteries should probably be drained no more than 10% on a daily basis.

“Hybrid” batteries or “Marine” batteries may be labeled deep cycle, but are something of an undesirable compromise.  “Gelled” deep cycle batteries offer a safer, less hazardous electrolyte in gel form but at a heftily increased price.  AGM (Absorbed Glass Mat) batteries incorporate a Boron-Silicate glass mat between plates.   Also called “starved electrolyte” batteries, the mats are partially soaked in acid.  These are less hazardous because they won’t spill or leak acid if damaged.  These sealed batteries also recombine oxygen and hydrogen back into water during charging.  The lifecycle of an AGM deep cycle battery typically ranges between 4 to 7 years.  Deep cycle Gelled and AGM type batteries can get pretty big and might cost well over $1,000 each when new.

All lead-acid automotive and deep cycle type batteries will eventually age or fail, but for a wide variety of reasons.  A normal automotive battery might age because lead dioxide flakes off the positive plate due to natural contraction and expansion during everyday discharge and charge cycles.  Shorts between plates, buckling of plates, loss of water, negative grid shrinkage, positive grid growth and positive grid metal corrosion can cause a battery to fail.  Battery aging can be accelerated by fast charging, overcharging, deep discharging, high heat and excessive vibration.  Acid stratification is a situation where weak acid is at the top and concentrated acid at the bottom of an automotive battery, and is a condition caused perhaps by a power hungry car that is not driven enough to fully charge its battery.  Sulfation is also caused by undercharging or by allowing a lead-acid battery to self discharge by sitting for a long period in an undercharged condition.   In a sulfated battery hard lead sulfate crystals will fill the pours and coat the plates.  In a few instances it may be possible to rectify sulfation in a battery but beware of false claims and salesmen selling snake oil.

* It is interesting to note that a lead-acid battery does not require sulfuric acid as an electrolyte, to work.   Alum (hydrated potassium aluminium sulfate) solutions work and alkali or base solutions may work as well.  An evident superiority of sulfuric acid is that it works as antifreeze by causing a significant freezing-point depression of water.   Alum solutions tend to crystallize as well as freeze.

Methanol fuel cell / NASA image

Fuel cells

Fuel cells are similar to batteries in that they convert chemical energy into electricity.  Like battery cells, fuel cells have anodes, cathodes and electrolytes.  The main difference between the two is that the chemicals are self contained within a battery’s cell(s) but must be imported or fed to a fuel cell.  A continual supply of fuel and of oxygen or another oxidizing agent must be fed or input to the fuel cell to perpetuate its chemical reaction and electrical output.   Methanol, natural gas or hydrogen perhaps from these are the most commonly used fuel cell fuels.

Although “fuel cell technology” may seem like new buzzwords in the automotive industry an Allis-Chambers tractor was driving around under fuel cell power more than half a century ago.   A Welshman invented the first fuel cell in 1839 and below is one of his sketches.

Of the several types of fuel cells designed thus far the electrolyte (whether it be liquid or solid) chosen determines the composition of the anode, cathode and usually a catalyst as well.   Alkali fuel cells use an electrolyte of potassium hydroxide, operate around 350° F and require an expensive platinum catalyst to improve the ion exchange.   A  Proton Exchange Membrane fuel cell uses a permeable sheet of polymer as its electrolyte, works around 175° F and also requires a platinum catalyst.   Platinum catalysts are also required for Phosphoric Acid fuel cells, which use corrosive phosphoric acid as the electrolyte and work at about 350° F.   High temperature salts or carbonates of sodium or magnesium are generally the electrolyte of choice in Molten Carbonate fuel cells.  These fuel cells work at a hot 1,200° F perhaps and employ a non-precious metal like nickel as the catalyst at both electrodes.   Hotter yet, Solid Oxide fuel cells require an operating temperature of about 1,800° F before the chemical reactions begin to work.  The electrolyte in one of these cells is frequently a hard ceramic compound of zirconium oxide and the catalytic activity is enhanced by the complicated composition of its electrodes.

Homemade Batteries

In a previous post Luigi Galvani, Alessandro Volta, the voltaic pile and Benjamin Franklin’s coinage of the term “battery” were discussed.   The image above shows several ways to construct simplistic batteries.  Each of these examples exploit dissimilar metals and an electrolyte that can be either acid or alkali based.

In the image above a potential and usable current should be created once an electrolyte is poured into the can, except for one problem.  Beer and soda cans are spayed with a plastic polymer coating to prevent interaction of the beverage with the metal, and this coating would interfere with ion exchange.  In a battery cell the current carrying capacity (or power) is governed by the area of the electrodes, the capacity is governed by the weight of the active chemicals and the cell voltage is controlled by the cell chemistry.  While a strong electrolyte might produce more voltage it would also eat through the very thin wall of the aluminum can sooner.

The notion intended by the image above is that a PVC pipe holds an electrolyte (preferably a mild mixture of bleach and water) and electrodes of copper pipe and tin solder are used.  Obviously the anode and cathode must not make contact but the closer they are suspended together- the better the ion exchange will be.   House wiring (just called “Romex” by some American electricians) comes in both copper and aluminum versions and could also be applied in this fashion.

To prevent sacrificial damage of the electrodes when this type of primary is not being used, it would be beneficial to be able to remove the electrolyte.  This image above suggests a way to connect PVC pipe together so that electrolyte could be added or removed when necessary.   Eight cells would produce 12v if their nominal voltage was 1.5 volts each.

The antique Daniell cell (above) probably could have gone without mention here except that some artistic types might find it interesting.  Looking to eliminate hydrogen bubbles, Daniell (1836) came up with a battery cell that used two electrolytes rather than one.   Originally, solutions of copper sulfate (deep blue in color) and of zinc sulfate (or sulfuric acid) were separated by a porous barrier of unglazed ceramic (or plaster of Paris, later used by Bird).  Operation of a single cell (2 half cells) worked fine until the porous barrier became clogged up with deposited copper.   Later a ceramic pot inserted inside a copper jar separated the two solutions.  Because of the flow of current the ceramic eventually became coated with copper.  Even later variations of the Daniell cell included the Bird’s cell and the gravity or crow’s foot cell.  In the gravity cell the difference in specific gravity of the two solutions is all that is necessary to keep them separated.  The containers of such cells should not be jostled.  Gravity cells were the favored source of power for telegraph stations especially in remote areas, for about 90 years.  Their zinc electrode resembled a crow’s foot, the batteries were easily maintained by replacing simple components – as needed.   Modern incarnations of the Daniell cell incorporate a “salt bridge” (either a glass tube filled with a fairly inert jellified solution of potassium or sodium chloride, or filter paper soaked in the same two chlorides).  When breaching two separate containers, the salt bridge completes the circuit – allowing only ions to flow back to the anode.

Solar energy at home

Most of the energy we earth bound humans consume comes directly from the sun, exceptions being atomic fission and some types of chemical reactions.  Fuel oil, coal and natural gas energy that civilizations use exist because of the Sun’s previous contribution in the formation of those hydrocarbons.  Wind currents are caused by the sun warming the air and as thermals rise they are displaced by denser, colder air.  Likewise the sun’s energy is ultimately responsible for distributing snow melts and rainwater water to higher elevations, which create the kinetic energy needed to power watermills and hydroelectric generators.  On a small personal scale, more individuals are learning to exploit the sun’s energy to heat their homes, generate their own power or to cook their food.  The two main methods of acquiring power from the sun are photovoltaic (PV) cells and thermal energy collectors.

Almost 53% of the energy in sunlight is absorbed or reflected before it even hits the surface of the earth.  The glazing or protective substrate in a solar collector can further diminish the amount of energy obtained.  Even the best solar panels can be considered to be inefficient.  The amount of energy collectible by a given solar panel is subject to many variables.  Whether talking about heat or electricity we generally measure that energy in units of Watt-hours (energy = power x time).  Under the best and brightest conditions a panel might collect as much as 2,000 Watts per sq. meter but under realistic or averaged conditions the expectation might only be half that.  During the daylight hours of a normal summer day at 40 degrees latitude, a solar collector would be doing good to average 600 Watts per sq. meter.  In wintertime for the same location the same collector might gather an average of only 300 Watts per sq. meter.  For any random location around the earth the average collectible solar energy per mean solar day (24 hours) is only about 164 Watts per square meter.

Overview of PV

In a photovoltaic solar cell an electrical charge is generated when photons excite the electrons in a semiconductor.  There are many types of solar cells and even some new developments in technology which will hopefully lead to the future manufacture of more affordable photovoltaic solar panels.  The warmer the photovoltaic solar panel gets the less power it can produce.  Essentially the temperature doesn’t affect the amount of solar energy a solar panel receives, but it does affect how much power you will get out of it.

The most common photovoltaic solar cells are made by chemically ‘doping’ a very thin wafer of otherwise pure monocrystalline (single-crystal) silicon.  In a delicate and complicated process of fabrication, wafers of silicone are generally cut or sliced as thinly as possible (before they crack) to a thickness of about 200-micrometers or the width of a typical moustache hair.  Since each individual solar cell produces only about 0.5V, several cells must be wired together to produce a useful photovoltaic array.  Mostly produced in China, commercial photovoltaic solar panels are very expensive, averaging $2 – $3 cost for every single watt they produce.  An average U.S. residence consumes something like 30.6 kWh per day, 920 kWh per month or 11,040 kWh /year.  In a country like the U.S. where grid power is comparatively cheap (averaging 10 cents per kWh in 2011) it would take a very long time for photovoltaic panels producing equivalent energy to pay for themselves.  In the meantime an individual with a “do it yourself” mentality can more directly utilize solar energy by fabricating his own contraptions to collect heat.

Solar Ovens

Although it would not be considered a quick process, it is easy to cook food with direct sunlight.  Slow cooking oftentimes creates superior dishes with the best blend of flavors.  Some heat trap type solar ovens can easily produce temperatures over 250 deg F; sometimes up to 350 deg F.  No matter what type of oven is used however (electric, gas, solar, smoke pit or Dutch) a good cook knows that slow cooking with a modest heat over a long period, will make an otherwise tough piece of meat more tender.

Essentially there are only two types of solar oven; those that entrap heat or those that reflect it.  To form a simple ‘heat trap’, a cardboard or wooden box can be insulated, spray painted black inside and then lidded with glass or clear plastic.   It helps when the cooking vessel itself is dark also – to better absorb solar heat.  In addition to being dark, it helps when pots are thin and shallow and have tight fitting lids.  Even glass mason jars make useful solar cooking utensils.  These can be spray painted black and the lids can be unscrewed a bit to allow vapor pressure to escape.   It might seem that parabolic or concave reflecting cookers would be complicated to construct, but some examples have been made by simply surfacing the inside of umbrellas or parasols with aluminum foil.  Mirrored Mylar or similar BoPET films are also useful materials in this type of application.  Doubtless many examples or ‘instructables’ detailing the construction of reflective type solar ovens, exist elsewhere on the Internet.  Some specially constructed reflective ovens claim to be able to reach temperatures of nearly 600 degree F.

The importance of cooking some foods, especially meats, is to kill bacteria.  Bacteria won’t grow below 41 deg F or survive above 140 deg F.  The internal temperature of meats needs to reach a range between 140 deg F and 165 deg F to be considered safe.  Seafood needs to be cooked to 145 deg F or hotter.  To rid poultry of salmonella, poultry must reach 165 deg F on the inside.  Egg dishes should reach the same temperature.  Trichinosis is halted by cooking pork to about 160 deg F.   Ground beef should reach 155 deg F for safety.

Solar stills

Back in the 1960’s a pair of PhD’s working in the soil hydrology laboratory for the USDA invented a solar evaporation still that could suck useful drinking water out of the ground.  Even in the arid desert around Tucson, Az. where they were located, they realized that the soil entrapped useful moisture.  Such a solar still is made by digging a pit in the ground, placing a collection pot in the bottom and covering the hole with a sheet of plastic.  Additional moisture could even be gathered by placing green vegetation under such a tarp.

It seems that the first evaporative solar stills were invented back in the 1870’s to create clean drinking water for a mining community as explained in an earlier post in this same blog named “The Nitrate Wars”.   This same distillation where moisture is evaporated before the condensation is collected, is employed in affordable, plastic-vinyl inflatable stills that can equip small boats and survival craft at sea.  Where once stranded fishermen and sailors faced a death by dehydration they now have the opportunity to create the drinking water they need from seawater.  Muddy or brackish germ infested groundwater can be reclaimed in the same way.

There are several possible techniques to employ and efficiency factors to consider when fabricating an evaporative solar still.  Obviously good direct sunlight is essential to their efficient functioning.  The ‘basin type” solar still is the most common type encountered and somewhat resembles a heat trap solar oven.  In a “tilted wick” solar still, moisture soaks into a coarse fabric like burlap and climbs the cloth before it eventually evaporates.  In higher latitudes ‘multiple tray’ tilted stills can be used, where the feed water cascades down a stairway of trays or shelves, allowing closer proximity to the glass and enabling steeper tilt angles for the panel to capture optimum sunlight.

Other liquids besides drinking water can be refined in an evaporative solar still.  Ethanol can and has been concentrated from mashes, worts, musts or washes using a solar still.   Since a distiller usually desires more direct control over temperatures however, he might consider solar stills to be practical only for so-called “stripping runs”.   Some of the earliest perfumes were created from fragrances collected by distillation.   Soaking wood, bark, roots, flowers, leaves or seeds of some plants in water before distilling the mixture, is a common way of obtaining aromatic compounds or essential oils.   Not all plant fragrances should be distilled but eucalyptus, lavender, orange blossoms, peppermint and roses commonly are.   The lightest fractions or volatiles of petroleum (like gasoline) separate at temperatures available in solar stills, but the heavier ones will not.  Theoretically it should be possible to place slip or crude oil into a solar still to separate out the gasoline and higher fractions.

Solar water & air heating

Most readers will have experienced how water trapped in a garden hose will get hot on a summer day.  Portable camp showers are simple black water bags, suspended at a little elevation and in direct sunlight to warm the water.

Where climatic conditions permit people may employ gravity fed or pump pressurized waterlines and tanks on rooftops or simply along the ground to achieve the same solar water heating effect.  Others may construct or install dedicated solar heating water panels to heat swimming pool water or to pre-heat water before it enters their home’s gas or electric water heating tank.

The construction of a solar water heater and a solar air heater can be very similar in concept.  Basically air or water is conducted through pipes or conduits to a panel where the heat exchange takes place.  Copper pipe might be the most desirable material to use in a solar water panel because of its pressure holding ability, resistance to corrosion and longevity.  Thin walled pipes of cheaper metals can be used to adequately exchange or transfer heat to air that passes through them.  A growing fad in the construction of homemade air-heating solar panels is to build the collector with empty aluminum beer or soda cans.  The tops and bottoms of the cans are punched or drilled out and the cans are glued together to form a continuous airtight pipes.  The box that holds everything is well insulated (sides and bottom) every interior surface exposed to sunlight is spray painted a dark, sunlight absorbing color – preferably using a high quality, high temp, UV protected paint.  A transparent glazing (of glass, plastic, fiberglass, Mylar, acrylic, polycarbonate, etc.) is tightly sealed over the top of the trap.  A double or even triple layer of glazing is preferable to a single one to reduce the escape of thermal heat.  While beer and soda cans are popular because of their availability and affordability, equally efficient collectors could be made from tin cans (made of metal called tinplate), rain gutter downspouts, old aluminum irrigation pipes, single walled stove pipes or even from bug screen like you’d find on a window.  This site, chosen from many that discuss solar heating with air, suggest that bug screen collectors are on par with soda can collectors and are possibly easier to construct.

In the choice of fan or blower used to push or pull air through the system, it is preferable to circulate a large volume of modestly heated air rather than a small quantity of thoroughly heated air.  Ideally a solar panel can increase the heat of the air passing through it as much as 50 or 60 degrees F.   In this type of collector an optimum airflow rate of 3 CFM per square foot of absorber has been suggested.  In general the larger the solar air panel, the better – small ones are probably not worth considering.  They should be built with quality paints, glazing and other components where possible to resist corrosion and decomposition from sunlight and other climatic elements.

Pointing solar panels

Direction

For optimum efficiency any solar panel should face the sun at a perpendicular angle.  The position of the sun changes constantly however throughout the day.  Some institutions or uber rich people might purchase solar trackers which employ servo or stepper motors to keep photovoltaic panels aligned with the sun.  Such ‘trackers’ increase overall efficiency by increasing morning and afternoon light collection.  The rest of us however have to make do with permanently fixed or periodically adjustable panel mounts.  Normally the bases of fixed panels are aligned perpendicular to due (not magnetic) south.  Some owners of grid tied solar photovoltaic panels however are deciding to aim their panels towards the west.

Tilt

The effectiveness or efficiency of a given solar panel is definitely affected by its proper orientation to the sun but as the sun moves around a lot, solar panels that do not automatically track its movement must seek a positional compromise.  The sun’s apparent altitude in the sky changes throughout the year.  Because of the earth’s motion the sun’s altitude appears to vacillate 23.5 degrees between summer and winter solstices or every 6 months.  Solar panels near the equator can be positioned parallel with the horizon and largely remain efficient by just pointing straight up.  The further a location is from the equator the more vertical a panel’s ideal tilt becomes.  Above the 45th parallel, vertically fixed solar panels mounted to the side of a building can preform admirably in the wintertime.  There is no one perfect tilt angle with which to keep a solar panel perpendicular with the sun’s rays throughout the year.  This fact motivates some people with adjustable panel mounts to periodically climb up on their rooftops with wrench in hand to refine panel tilt.  Others might wish to install a solar panel permanently in the best year round average position and not worry about adjustments.

Older literature for solar panel installation might quote a rule of thumb where 15 degrees are added to latitude for wintertime panel tilt, or 15 degrees of angle are subtracted from latitude to acquire summertime panel tilt.  A more modern set of calculations being mimicked or repeated often around the web, suggest wintertime tilts that are a bit steeper than common to capitalize on midday rather than whole day solar gathering and flatter than normal summertime tilts favoring better whole day rather than midday collection.

-To calculate the best angle or tilt for winter:

(Lat * 0.89) + 24º = ______   (The latitude is multiplied by .89 and added to 24 degrees)

-The best angle for spring and fall:
(Lat * 0.92) – 2.3º = ______

-The best angle for summer:
(Lat * 0.92) – 24.3º = _____

-The best average tilt for year round service:
(Lat * 0.76) + 3.1º = _____

For the purpose of illustration a latitude of 35 degrees North will be chosen.   Locations somewhat close to this latitude include: the Straight of Gibraltar, Tunis Tunisia, Beirut Lebanon, Tehran Iran, Kabul Afghanistan, Seoul Korea, Tokyo Japan – and in America, cities along Interstate 40 or the old Route 66 (Raleigh NC, Memphis Tennessee, Fort Smith AR, Oklahoma City OK, Albuquerque NM, Flagstaff AZ and Bakersfield CA).

 

A couple of sources for more information:

http://www.solar-facts-and-advice.com/

http://www.nrel.gov/rredc/solar_data.html

 

 

Water Turbines

The Egyptians were using mechanical energy to lift water with a wheel in the 3rd century BC.   Four hundred years later in the 1st century AD Greek, Roman and Chinese civilizations were using waterwheels to convert the power of flowing water into useful mechanical energy.   The word “turbine” was coined from a Latin word for “whirling” or “vortex”.  The main difference between a water wheel and a water turbine is usually the swirl component of the water as it passes energy to a spinning rotor.  Although the Romans might have been using a simple form of turbine in the 3rd century AD, the first proper industrial turbines began to appear about 200 years ago.  Turbines can be smaller diameter for the same power produced, spin faster and can handle greater heads (water pressure) than waterwheels.  Windmills and wind turbines are generally differentiated by the reasoning that windmills turn wind-power into mechanical energy whereas ‘wind turbines’ convert wind-power into electricity.  This post attempts to reveal to those individuals with an exploitable water source that – modest advancements in ‘micro’ hydro technology have made it feasible for them to potentially create useful power from low water heads or from very modest water sources.

Above the horizontal undershot waterwheel requires the least engineering and landscaping labor to install; the width of the runner can be tailored to match the flow rate and only a small water ‘head’ is required.  The ‘breastshot’, ‘overshot’ and ‘backshot’ styled waterwheels get progressively more efficient.

*  Water head can be thought of as the weight of water in a static column.  Since fluids don’t compress, the weight of water in a pipe is directly related to its pressure at the bottom (measured as psi or pounds per square inch).  As a stream drops in elevation its head is a measurement of that drop.  Water weighs 62.427 lbs per cubic foot.  There are 1,728 cubic inches in a cubic foot.  A cube of water 12” high, 12” wide and 12”deep would have a psi of ((62.427 / 12) /12)  or 0.433 lbs. per square inch.   Any column of water 1 ft. high, regardless of width, still has a water head of 1 ft. and a psi of 0.433 lbs/in².   Water drop is simply multiplied by the constant 0.433 to determine the potential psi. 

Boyden turbine

A Frenchman named Fourneyron invented the first industrial turbine in 1827.  The idea was brought to America and improved upon in the form of the Kilburn turbine in 1842.  By 1844 a conical draft tube addition resulted in the Boyden turbine.  There were dozens of Boyden turbines in operation in northeast America by the time radical abolitionist John Brown raided Harper’s Ferry in 1859.   Located at the confluence of the Shenandoah and Potomac rivers, Harper’s Ferry was a national armory and a beehive of activity where gunsmiths made small arms.   In 1859 at least 2 Kilburn and 5 Boyden turbines were driving the  jack-shafts and belts needed to the power lathes, sawmills and other equipment necessary to keep 400 employes busy at the armory.

Fourneyron’s turbine and subsequent Kilburn and Boyden types were further followed themselves by increasingly efficient  turbines including:  the Leffel double turbine, John B. McCormick’s mixed-flow turbine, the New American and Special New American turbines.  All of these are known as outward flow reaction turbines (which are reminiscent of cinder, sand or fertilizer spreaders – but with water spraying out at the bottom).

A different type of turbine called an inward flow (or radial flow) reaction turbine was developed by James b. Francis in 1849.  In the snail shaped Francis turbine water is sucked into a spiraling funnel that decreases in diameter.  Used at the beginning of the 20th century mainly to drive jack-shafts and belts for machinery in textile mills, Francis type turbines soon became the type favored for hydroelectric plants and are the type most frequently used for that purpose today.  This photograph which was apparently taken in Budapest before 1886 shows what looks to be a Francis turbine being installed in the vertical axis rather than the horizontal axis.

A “runner” is that part of a turbine with blades or vanes that spins.   As with any other turbine the scale of dimensions can be adjusted up or down to suit individual needs.   Although small Francis turbines are produced the ones used in large hydroelectric power stations are impressively huge – some producing more than a million horsepower each (1,341 hp = 1 Megawatt).   The largest and most powerful Francis type turbines in the world are in the Grand Coulee Dam (Washington USA).  The runners of the turbines there have diameters of 9.7 meters and are attached to generators producing as much as 820 Mw each.   China’s Three Gorges Dam is capable of the world’s largest electrical output however with 32 main generators producing an average 700Mw each for a total 22,500 MW optimum output.   Located between Brazil and Paraguay the world’s second largest dam (in terms of generating capacity) is the Itaipu dam with 20 Francis  turbines powering 700 MW generators.   In 2012 and 2013 Itaipu’s annual electrical output actually surpassed that of Three Gorges due to the amount of  rainfall and available water.

Another type of reaction turbine was developed by an Austrian in 1913 looks like a boat propeller.  Some windmills are called Kaplan turbines.  The blades or vanes on a Kaplan designed hydro turbine are adjustable, allowing the turbine to be efficient at different workloads or with varying water pressures.  Although complicated and expensive to manufacture, the Kaplan design is showing up more frequently around the world, especially in projects with low-head, high flow watersheds.  They can be found working in the vertical or the horizontal planes.  Large Kaplan turbines have been working continuously for more than 60 years at the Bonneville dam.  The Bonneville dam is on the Columbia River between Washington and Oregon, several hundred miles downstream from the Grand Coulee dam.  Both dams were started at the same time during the depression and were initiated by Roosevelt’s (FDR’s) “New Deal”.  Small inexpensive Kaplan turbines (without adjustable vanes) can be made to work in streams with as little as 2 feet of head.

The so called “Tyson” turbine looks like it could qualify as a Kaplan turbine but  this modern example of micro hydroelectric technology encases its own generator in a waterproof housing.  The unit is submerged into a stream and usually suspended from a small tethered raft.  The stream can be shallow but obviously a high flow rate will encourage the best electrical generation.

Yet another type of water turbine is tenuously referred to as a “crossflow turbine”.   In the early 1900’s two individuals on opposite sides of the world independently contrived about the same turbine design.  A Hungarian professor named Banki and an Australian engineer named Mitchell invented turbines that combine aspects of both a reaction (or constant-pressure) turbine and an impulse (or free jet) turbine.  The runner of a Banki -Mitchell (or Ossberger)  crossflow turbine is cylindrical and resembles a barrel fan that one might find in a forced air furnace or evaporative swamp cooler.  The design uses a broad rectangular water jet that travels through the turbine only once but travels past each runner blade twice.  The moving water has two velocity stages and very little back pressure.

Most suited to locations with low head but high flow, low-speed cross flow turbines like this have a flat efficiency curve (the annual output is fairly constant and not as much affected by fluctuating water supply as are some other designs).  Large commercial crossflow turbines are manufactured that can handle 600 ft. of head and produce 2,500 hp.  Small homemade Banki – Mitchell units have been constructed that are capable of producing about 400 watts using a car alternator with 5.5 CFS (cubic feet/sec) of water from a stream with a head of only 33 inches.  These units can make considerable noise, so to keep vibrations minimized these turbines should be well balanced and spun at moderate revolutions per minute.

Two rising celebrities in the world of mini or micro hydroelectric technology are both impulse turbines.  The Pelton wheel or runner works in the vertical plane usually, and the somewhat similar Turgo in the horizontal.  Water pressure is concentrated into a jet that impacts spoon shaped cups of the Pelton or curved vanes of the Turgo.  These systems capitalize on high head, low flow water sources.  Turgo runners are sometimes quite small (like 3 or 4″ in diameter) and are designed to run at high speeds.   A small uphill water source and enough penstock (piping) to reach it are the main requirements necessary to make one of these small impact turbines useful.   Under the right circumstances a small Pelton or Turgo wheel of just a few inches in diameter is capable of producing perhaps 500 watts.   In the absence of running streams, snow pack or plentiful rainfall an individual living in a mountainous area might still be able to collect up-slope groundwater from perforated pipes buried in boggy areas, springs or the drainage ditches alongside roads.  A long run of water hose, polyethylene or polyvinyl chloride (PVC) pipe could conduct the water down slope, which would gain another pound per square inch of pressure for every 2.31 feet of drop.  Water catchment from barn and house roofs could be redirected to holding cisterns and used by these little turbines when appropriate to augment other alternative off-GRID power systems.

Built 1901 – used to power the mining town of Victor, CO. Courtesy of Gomez.

The Pelton wheel was patented in 1880 but Lester Allan Pelton actually got the idea from using and examining similar Knight water wheels in the placer mining gold fields of 1870’s California.  Employing fluid often diverted by sluices to a holding pond before being collected into a penstock and dropping further, miners washed entire hillsides away with jets of high pressure water.  The tip end of this water cannon was a nozzle called a “monitor” and there was no ‘off button’.  Most of these hydraulic mining monitors spewed water around the clock so it was probably just a matter of time before some enterprising miner attempted to convert that wasted energy into a useful mechanical energy by spinning a wagon wheel with pots and pans attached to its rim.  While ‘Knight wheels’ (the 1st impact water turbines) were originally constructed to power saws, lathes, planers and other shop tools some were actually used in the first hydroelectric plants built in California, Oregon and Utah.  Lester Pelton’s innovation was to extract energy more efficiently from a water jet by splitting the cup and deflecting the splash out of the way.

Between the 1870’s and the 1890’s innovations for both hydroelectric turbine and alternating current development were occurring at breakneck pace.  The first hydroelectric power schemes began to appear after 1878 onward and for several years created only DC current.  In three years between 1886 and 1889, the number of hydroelectric power stations in the U.S. and Canada alone quadrupled from 45 to over 200.  AC development milestones during this period include: step up and step down transformers, single phase, polyphase or triple phase AC, and great improvements in the distance of power transmission.   <This site> provides an interesting history and timeline on the maturation of AC power.

The Ames hydro electric power plant in Colorado claims to “be the world’s first generating station to produce and transmit alternating current”.   Perhaps that claim should be amended to specify only “AC for industrial use”.  Originally the Ames plant attached a 6 foot tall Pelton wheel to a Westinghouse generator.  The largest generator ever built up to that time, it made 3,000 volts, single phase AC @ 133Hz.  The Pelton wheel was driven by water from a penstock with a head of 320 feet.  The power was transmitted 2.6 miles to an identical alternator/motor, driving a stamp mill at the Gold King Mine.  The mine owners chose this newfangled electricity over steam powered machinery because of the prohibitive cost of shipping coal by railway.  In 1905 the Ames power plant was rebuilt with a new building, two Pelton wheels with separate penstocks from two water sources and a General Electric generator of slightly less output capacity.  After 123 years this facility’s impact turbines are still producing electricity.

The success of the Ames power plant along with a well done 1893 World’s Fair exhibit by Tesla and Westinghouse helped determine a victor in the famous “War of the Currents” and more immediately, who would win the prestigious Adam’s power station contract soon to be constructed at Niagara Falls.

The main characters in the ‘War of the Currents’ were (from left to right above) the DC proponents Thomas Edison and J.P. Morgan and their AC rivals Nikola Tesla and George Westinghouse.  Pride, patents, reputations and big money were at risk in this somewhat ridiculous conflict.  At its peak the quarrel was exemplified by Edison going about the country and staging demonstrations wherein he electrocuted old or sick farm & circus animals with ‘dangerous’ AC current.  It is rumored that the electric-chair used for executions was itself created due to a secret bribe from Edison.  In response Tesla staged some carefully controlled demonstrations where he shocked himself with AC to prove its safety.  In truth both DC and AC currents are potentially deadly at higher voltages, but AC may ‘win out’ slightly because its alternating fluctuation might induce ventricular fibrillation (where the heart looses coordination and rhythm).

* For those that may not know: Edison was a prominent inventor who formed 14 companies and held 1,093 patents under ‘his’ name although his formal education consisted of only 3 months schooling.  The largest publicly traded company in the world (General Electric) was formed by a merger with one of Edison’s companies.   JP Morgan was one of the most powerful banker/ financier/ robber barons in the world in the 1890’s.   JP reorganized several railroads, created the U.S. Steel Corporation, and bailed the government and U.S. economy out of two near financial crashes – once in 1875 and again in 1907.  He was also self conscious about his big nose and did not like to have his picture taken.   Recognized as a brilliant electrical and mechanical engineer Tesla never actually graduated from his university.  Immigrating to the U.S. in 1884, Tesla even worked for Edison before the two had a falling out.   Westinghouse attended college for 3 months before receiving the first of his 100 patents and dropping out.  He went on to found 60 companies.  

Although AC has been the favored method of current transmission for the last century, in the War of the Currents, DC power never fully capitulated.  Considering storage benefits, DC may someday stage a spectacular comeback.  In Cities like Chicago and San Francisco an old DC grid may run parallel to its AC complement.  Most consumer electronics convert AC into DC anyway.  DC offers some advantages over AC, including battery storage which provides load leveling and backup power in the event of a generator failure.  There is no convenient way to store excess AC power on the GRID so it is shuffled around for as long as possible.

Alternating current originally offered advantages over direct current in its ease of transmission.  High voltage / low current travels more efficiently in a wire than low voltage / high current will.  The introduction of the transformer (which works with AC but not DC) allowed AC to be “stepped up” to a higher voltage, transmitted and then stepped back down to usable power at the destination.  DC current (under the Edison scheme) had to be generated very close to its finial destination or otherwise use expensive and ungainly methods to achieve transmission over longer distances.  Voltage drop (the reduction of voltage due to resistance in the conducting wire) affects both currents equally.  Due to resistance, some power will be lost as heat during transmission.  AC suffers from a resistance loss during transmission that does not affect DC.  “Skin effect” is the tendency of AC to conduct itself predominately along the outside surface of a conductor rather than in the conductor’s core.  The whole wire is not being used – just the skin.  This skin effect resistance increases with the frequency of the current.  This phenomenon along with new technology for manipulating DC voltages has recently encouraged several companies to construct new High Voltage Direct Current (HVDC) power lines for long distance transmission.  The Itaipu Dam mentioned earlier for example transmits HVDC over 600 kV lines to the São Paulo and Rio de Janeiro – some 800 km away.

The huge dam projects of the 1930’s in the U.S. were not created to provide electrical power to customers, but were primarily intended to redirect water for the purpose of agriculture.   Even today the bulk of power created by those dams is used to pump water back uphill so that it can be broadly distributed by irrigation.  In 2008 the U.S. Energy Information Agency (EIA) estimated that only 6% of the nation’s power was generated hydroelectrically and that amount has changed little in the last 5 years.  The EIA  does predict a growth in the future for photovoltaic and wind generated power.  Canada with a much smaller population supplies itself with a greater percentage of hydroelectric power than the U.S. and also has more kinetic energy available in terms of exploitable water resources.

– Wind turbines, water turbines, Archimedes screws and centrifugal pumps in reverse can be mounted to the same types of alternators or generators.  Small or miniature turbines can be affixed to a wide range of DC motors from tools, toys, treadmills, electric scooters, old printers, stepper motors and servos.  Commonplace AC induction motors from laundry machines, blowers, furnaces, ceiling fans, tools and other sources can be converted into brush-less low rpm alternators by rewiring or installing permanent magnets in the armature.  Usually but not always in a modest off-grid power scheme AC current from an alternator or magneto needs to be rectified into DC so that the energy can be stored in a deep cycle ‘battery sink’.  Automotive alternators contain their own rectification but these are less than ideal for turbines for a couple of reasons.  Charge controllers and inverters are also pertinent subjects in the discussion of alternate energy.  These topics may be addressed in some future post.  For now a final image (of a rectifying ‘full wave bridge’) and some miscellaneous video links are offered.

CIVIL 202 – Pelton wheel project –  3 minute video – school science project

Micro Hydro Electric Power- off grid energy alternatives – 7.5 minute video – something of an advertisement

Home Made Pelton Wheel – rather long 12 minute video

Turning Green In Oxford – 9 minute video / power by Archimedes screw

Algonquin Eco-Lodge – 8 minute video – generating by reversing water flow through centrifugal pump

————————————————-

  Added – July 2021  Two videos displaying antique water powered gristmills working. The first video is short and sweet with no talking (3:20 min). The second video is very verbose with detailed explanation, and long (22:00 min).

George Washington’s Gristmill at Mount Vernon

The Old Fashioned Way Ep02 ‘Wayside Inn Grist Mill’

————————————————

Hot Stuff 2

Bronze & Brass

As the ancients toyed with fire they created glasses and ceramics and discovered several metals.  In antiquity only about 7 elements (gold, copper, silver, lead, tin, iron and mercury) were recognized as being metals.  Although their ores were used to create alloys – arsenic, antimony, zinc and bismuth were not determined to be unique metals until the 13^th or 14^th centuries AD.  With the addition of the discovery of platinum in the 16^th century (ignoring the Incas who were apparently smelting it earlier) that makes a total of only 12 unique metals (out of 86 known today) mankind recognized before the 18^th century AD.   Gold and copper were the first metals to be widely used.  Because of their low melting points the first metals to be smelted however might have been tin and lead.  Lead beads unearthed in Turkey have been dated to about 6,500 B.C.  Galena (lead ore) is fairly common and widely dispersed whereas tin oxide (as in cassiterite SnO2) is relatively rare.  Neither gold, copper, tin nor lead however were as influential in the course of human events as was bronze; a hard alloy which upon occasion has been mixed from all four simultaneously.

The progression of mankind’s technological advancement is broadly categorized into the Stone, Bronze and Iron Ages, the Renaissance, the Industrial Age and presently what some are pleased to refer to as the “Information Age”.  Erudite scholars from some future millennium however may look back and call ours simply – the “Plastic Age”.   The “Bronze Age” is subjective term depending upon location or culture but it implies the mining and smelting of copper that has been hardened with an alloy to make bronze weapons and tools.  The Bronze Age occurred around 3,150 BC (or BCE) in Egypt, 3,000 BC in the Aegean area, 2,900 BC in Mesopotamia and about 1,700 BC in China.   Gold, copper, lead (and silver to a lesser degree because it is found in the same galena ore which produces lead) metalworking dates from about 6,000 BC onward and so actually predates the so called ‘4^th millennium BC – Bronze Age’.   The first gold and silver coinage comes much later in the 7^th century BC in Lydian, Persian and Phoenician cultures.   The first exchangeable copper coinage might have appeared in Greek and Roman societies.

native copper
http://commons.wikimedia.org/wiki/File:NatCopper.jpg

* Both copper and silver ions are germicidal and can inhibit or kill bacteria in water.   The ancient Egyptians employed copper medicinally.  Some modern hospitals incorporate copper in the form of water faucets and doorknobs.

Copper Alloys

We usually think of bronze as being an alloy of copper and tin and brass as being merely an alloy of copper and zinc but as usual the real picture is more complicated than that.  There are many alloys of copper that are called bronze or brass and occasionally the distinction is not clear.  There is tin bronze, leaded tin bronze, manganese bronze, silicone bronze, phosphor bronze, aluminum bronze, arsenic bronze and beryllium copper.   ‘Red brass’ copper alloy historically used for casting cannons actually contains about 5 times more tin than it does zinc.  Many modern coins (like the American dime, quarter and half dollar) have a copper core sandwiched between two layers of cupronickel (an alloy of 75% copper & 25% nickel).  The Swiss franc and American nickel (5 cent piece) are actually solid homogenous cupronickel.   There are a large number of distinctly recognized mixtures of brass as well.  ‘German silver’ (or nickel silver or nickel brass) is similar to afore mentioned cupronickel but contains about 2% zinc.  ‘Muntz metal’ (copper, zinc and a trace of iron) is an alloy thought up a couple of centuries ago to provide a cheaper ship hull protective sheathing than the copper one which it replaced.   ‘Nordic gold’ is an alloy of 89% copper, 5% aluminum, 5% zinc, and 1% tin – that is used in several Euro coins.

Two Egyptian bronzes
source: Google free to us or share filter

The first bronzes were arsenic bronzes.  While this might be attributable to the fact that the copper ores then smelted usually contained some indigenous arsenic, at some point early metalworkers deliberately added more arsenic to make a harder alloy.  Arsenic bronze is much harder than the original – excessively ductile copper and allows for the creation of useful tools, weapons, body armor and sculptures that will stand up under their own weight.  At some later point in history, tin gradually supplanted arsenic as the preferred alloy for bronze.  Tin bronze is not harder or mechanically superior to arsenical bronze.  It is likely that tin ore (which was scarce and required many civilizations to acquire it by trade) produced an alloy that required less work hardening to produce a sharp sword or an alloy that would fill a casting faithfully without leaving voids.  Arsenic sublimates (does not melt) at a temperature lower than molten copper and some arsenic oxide could be lost during casting.  Arsenic vapors are unhealthy and can attack the eyes, lungs and skin.  The use of tin probably afforded more control over the forging and casting processes.

* Arsenic (atomic element #33) is a metalloid that is used to harden both copper and lead.   Modern lead/acid car batteries usually feature some arsenic as well as some antimony within their lead components.  Long called the “Poison of Kings and the King of Poisons” arsenic is also a common and widespread groundwater contaminant.  Arsenic compounds were used as a vesicant (blistering agent) and or vomiting agent in Lewisite and Adamsite gasses used after WWI.   Arsenic is also used in the green pressure treated wood preservative known as CCA (Chromated Copper Arsenate).  Within CCA copper acts to slow the decay caused by fungus and bacteria, arsenic kills insects and chrome just helps bind or fix the other two to the wood.   When used as a discreet poison the “poudre de succession”  is not deadly in small amounts but can stay in the body and accumulate before it becomes lethal.  Two early developed analytical test in forensic toxicology were concerned with determining the presence of arsenic, namely the Marsh test and the Reinsch test.  Significant concentrations of arsenic in ground water are found in parts of New England, Michigan, Wisconsin, Minnesota, both Dakotas, Bangladesh, Vietnam, Cambodia, and China.

 * In ancient times lead was too pliable or ductile a material to make useful tools but that very characteristic allowed the Greeks and Romans to hammer and roll plumbing pipes to conduct water.  In Rome lead was used to line water cisterns or to pipe water to public drinking fountains or into the homes of the very rich.  In Rome the possibility of lead poisoning would seem to have been greatly reduced due to calcium buildup within the pipes.  Rome sits upon or near large limestone and travertine deposits.  A better source of lead poisoning if one were to be elected would be from lead dinnerware and acidic foods.   Wine for instance can easily leach toxic lead from goblets and cups.  

* Incidentally, bronze swords were often preferable to wrought iron swords.  Even in Roman times, officers commonly carried bronze weapons while the rank and file carried iron weapons.  Perhaps bronze swords were superior or simply more prestigious than their iron counterparts because they looked less crude and did not rust.  The Hittites (c.2000 – 1200 BC) are generally regarded as being the first iron-smiths.  Although their iron weapons were less brittle than hardened bronze weapons, these still had to be beaten or wrought from a bloom of roasted, not melted ore.  The inability to cast iron with a socket complicated the attachment of spear and arrow heads to their shafts.  It took about 3,000 years for furnace smelting technology to progress from copper melting temperatures to iron melting temperatures.  The first iron ore to be exploited was probably “bog ore” – a precipitate of iron oxide found in marshy areas, created by bacterial action and the decomposition of iron minerals.  Gradually the mining of rich hematite and magnetite ores occurred.   The Greeks used wrought iron beams in the construction of the Parthenon (between 447 – 432 BC).  The Romans occasional used T-shaped wrought iron girders in construction (as in the Baths of Caracalla).  Eventually it was realized that the carbon from charcoal created a stronger iron (steel).

the “Artemision Bronze” – circa 460 BC
source: Google free to use or share filter

The Greeks were masters of bronze casting.  Although the Greeks probably cast as many bronze sculptures as they chiseled from stone, the stone statues have remained where the bronze statues have not.   Every time a new war came along, bronze statues were hacked to pieces to provide the valuable metal needed to forge new weapons and body armor.   Very few Greek bronze statues have survived the ages and those that have been discovered in modern times (as in the image above – excavated in 1928) have been found underwater.   The Greek “Riace bronzes” date from about 460-450 BC and were discovered by a snorkeler just offshore of Riace, Italy in 1972.  A link is provided to this website because its fine pictures of the Riace bronzes can be enlarged.

Bronze alloys used for casting have the innate ability to expand slightly before they set and therefore all the fine nooks, crannies and scratches inside a mold are filled in with detail.  Life-sized hollow sculptures were made by a process known as the “lost wax process” (or as “investment casting” in jewelry-making or  industrial vernacular).

Horses of St Mark’s or “Triumphal Quadriga”
from fotopedia image: courtesy of Nick Thompson

It has not been determined if the horses of the “Triumphal Quadriga” are of Greek or Roman origin.   They are presumed to date to the 4th century BC and were stolen from the hippodrome in Constantinople where they had long resided, by Venetian troops following the Fourth Crusade (1202 -1204).   Napoleon stole the horses from the Venetians in 1797 and took them to Paris but they were returned to St Mark’s Basilica in Venice following the Battle of Waterloo in 1815.

Corinthian helmet : 500–490 BC
http://en.wikipedia.org/wiki/Corinthian_helmet

The iconic Greek Corinthian bronze helmet is an enigma to modern intellectuals because they can’t determine how it was constructed.  Our understandings of the construction of other helmet designs of the period are less controversial.  Neither the process of casting nor forging by hammer stroke alone adequately explain how the classical Corinthian helmet was built.  The best explanation seems to be that it was a product of both.

Most bronze or brass alloys are denser and heavier than iron or steel.  In the 17^th century almost all naval guns and terrestrial cannon were cast in bronze.  Bronze was the best material for the purpose but while being more durable than iron, it was also more expensive.  With the beginning of the 18th century, technology allowed the displacement of bronze artillery with more affordable cast iron pieces needed to supply growing armies and navies.  The weight of cannon and their placement aboard fighting ships (heaviest at the bottom) was an important consideration but weight was perhaps a more important concern for armies that had to tote them over hill and dale, streams and rivers.   Early French cast iron naval guns were notoriously dangerous and exploded with frequency while British, American, Swedish and Russian cast iron naval cannon were usually much superior.

The famous or iconic American Liberty Bell is an interesting story in bronze failure.   The metal in the Liberty Bell was cast not once, but three times: first in an English foundry when the bell was commissioned by the Pennsylvania Assembly in 1751, and then twice again by American foundry workers John Pass and John Stow.  The bell has a diameter of 12’ around its rim and weighs 2,080 lbs.  The bronze composition consist of 70% copper, 25% tin and a remainder a mixture of lead, zinc, gold, silver and arsenic.  The bell gained its moniker “Liberty Bell” from zealous abolitionist in the 1830’s, not from association with the Revolutionary War.  The one ton bell traveled or toured a lot considering its weight and there is disagreement over when its crack began.  Vigorous ringing encouraged a hairline fracture in the brittle alloy to grow into a wide crack.  The Liberty Bell rang last on Washington’s birthday in 1846, its sound after that no longer being acceptable.

The first brasses seem to have appeared somewhere around 500 BC and are sometimes referred to as calamine brass (calamine is zinc ore containing zinc carbonate or zinc silicate).  In early brasses calamine ore was introduced to molten copper and the zinc was readily absorbed, producing an attractive and useful alloy.  Zinc melts at 787 °F which is a temperature not much greater than that required to melt lead and which can be produced by a simple campfire.   Zinc boils and turns to vapor at 1,665 °F (907 °C) which is still lower than the 1,984 °F temperature needed to turn copper into a liquid.   For a long time not appreciated as a metal because heat caused it to escape as a vaporous gas, zinc production did not begin until about the12^th AD century in India, the 16^th century in China and (in large scale production) after 1738 in Europe.   In modern day zinc smelting, zinc sulfide is first roasted into an oxide called ‘zinc calcine’.   From there either electrolysis or any one of several complicated processes involving sintering (the electrothermic fusing of powders) or even the distillation of zinc fumes might be employed to retrieve the metal.

What usually distinguishes a brass from a bronze is the presence of zinc and a brighter or attractive golden color.  Brass is a softer, more malleable alloy than bronze and has some properties that make it uniquely desirable for some applications. Brass is used in bearings, gears, valves, locks, keys, doorknobs and clothing zippers because it has a low friction coefficient.  Brass does not spark as other metals might when struck.  Because of its desirable acoustic qualities and malleability, brass is the favored material for several musical instruments – especially horns.  Brass is the favored material in ammunition cartridge casings for a couple of reasons.  First, brass has the capacity to expand and contract quickly.  When a cartridge is fired in a firearm, the brass expands to fill the breach and prevents hot gasses from escaping rearward.  The brass then contracts to allow the casing to be ejected.  This action occurs quickly enough to allow for high cyclic rates of fire in machine guns.  Also brass’s softness and low friction attributes work more fluidly and cause less wear in the firearm’s steel mechanism than would any other metal.  While lead might be added to bronze to improve cast-ability, lead is added to brass to improve machine-ability.  California mandates that manufacturers of brass keys employ no more than 1.5% lead within keys sold in California, or otherwise label the product as potentially hazardous.

Do it Yourself

If the ancients were able to smelt copper, iron, gold and silver gold eons ago it seems reasonable that a lone individual should be able to duplicate that feat today.  Someone attempting to melt copper for instance will soon realize that it is not a simple task and that it takes concentrated energy to accomplish.  Above is an image of the bottom half of a homemade crucible furnace, the top has been temporarily removed.  In the center of a charcoal fire sits a crucible made from a scrap of square steel tubing that has had a bottom and two links of chain (for lifting) welded to it.  On the right side a rusty steel pipe conducts forced air from a hair drier into the bottom of the fire.

Above is the mold for the same bottom section of this crucible furnace, made from a plastic flowerpot and some tin cans.  A refractory mix was poured or tamped into the bottom 2” of the mold and allowed to dry, anchoring the wire reinforcement.  The tin cans were placed and now the mold is ready to receive more refractory cement between the large can and the plastic flowerpot.  Refractory is simply a building material that retains its integrity at high temperatures.  The refractory used was a mix of sand, Portland cement, fireclay and Perlite.  The ratios of the constituents used closely resembled this recipe.

Above is a downward image of the mold and a view of the finished result.  Note that on the left a bolt passes through a small hole in the set (or dried) bottom layer of refractory.  Presumably if the crucible were to leak during a cook, the molten metal should be able to run out the bottom and not be stuck in the bottom of the furnace.

A few notes about this furnace:  

– Even while the crucible and metal it held were white hot inside, the lid could be removed with bare hands – if done quickly.

– Fire at this heat combined with the forced air is very destructive of steel crucibles, both inside and outside.  Big flakes of iron oxide are almost guaranteed to sluf off and fall into and contaminate your precious metal.  The best crucibles are made of porcelain or graphite.

– The forced air should enter the furnace at an angle to encourage a whirl or vortex within the fire. 

– Although stoneware ceramics are fired and glazed at temperatures exceeding the melting point of aluminum, brass and copper, such ceramics cannot withstand such a rigorous acceleration in temperature.  You can expect a stoneware coffee cup crucible to shatter in a matter of minutes in such a furnace.

– The interior dimensions of this furnace are a bit too small to acquire a useful copper-melting heat from coal or charcoal alone.  There is simply not enough room for a crucible and enough charcoal at the same time.  Propane or waste oil would be better fuels for a furnace of this interior dimension.  These fuels can be introduced into the air pipe before it enters the furnace.  In the case of waste oil (any used automotive oil, diesel fuel or vegetable oil), it can be gravity fed, its viscosity potentially reduced by a lighter volatile or fraction, regulated by a simple valve and / or forced by a little additional air pressure.   

Jewelers crucible
File source: //commons.wikimedia.org
compliments of GOKLuLe

With a little effort an interested reader can find a wealth of information and instructables about crucible furnaces on the Internet.  Here are a few links to help such a reader get started.

In this video the furnace is constructed of stacked firebricks.   Brick furnace in snow.

This guy provides a good 3 part series on the construction of a backyard foundry.  In this video however he constructs his own graphite crucible.   Most people might simply purchase a graphite or porcelain crucible.  It is not necessary for a novice to go through all this trouble, but the information presented is useful.  “Making a Graphite Crucible“.

This video features a rather large furnace, requiring two men to handle the crucible.  “A Brass Casting Demonstration“.

——–

If there is a Hot Stuff part 3 to come in the future it will discuss ceramics and glass.

Hot Stuff – metal, ceramics & glass

How hot is HOT?   

   While physicist agree upon an absolute lowest temperature (absolute zero – where even subatomic particles don’t move) there is no consensus or formally defined limit for a maximum temperature.  The best approximation of maximum temperature might be Planck temperature (1.4168 × 10^32 Kelvin).  That’s about 100 million million million million million degrees in other words.  Within a thermonuclear bomb a temperature of 50 million °C is needed to initiate the fusion of a deuterium and tritium tamper.  The temperature at the core of our sun is assumed to be about 15 million °C.  The fission bomb “Little Boy” dropped on Hiroshima generated a heat of about 299,726 °C at its core.  The surface of the sun and the earth’s inner core are both much cooler at about 5,778 K (5,505 °C) each.   We have no instruments like thermometers or thermocouples to physically measure even these relatively low temperatures but instead must rely upon idealized thermodynamic theory to extrapolate these numbers.   

Hot Iron and Steel (first)

   Through chemical decomposition, oxidization and other natural processes happening over geologic time, few metals are found physically in metallic form.  Most of the earth’s retractable metals are dispersed as small flakes or inclusions within an ore of some type.  Since gold, copper, silver, and metals of the ‘platinum group’ are not very reactive chemically, early man was occasionally able to find bits of these “native metals” just lying upon the ground.  Mankind likely first encountered metallic iron however, in the form of a deposited meteorite.

Humankind’s technological advancement through the early ages is typically categorized by its tool making progress.  An archeologist considers tools of the ‘Neolithic Age’ to be more complicated than those of the general “Stone Age” – but less so than those of the ‘Bronze Age’ (some may distinguish between Copper and Bronze ages because the latter infers the more sophisticated smelting of alloys).  It took primitive civilizations about 3,000 years to progress beyond the Bronze Age to the “Iron Age” alone.  Also associated with or occurring concurrently with a period’s tool making technology were changes in religion, artistic styles, agriculture and societal structure.

Beyond about 9,000 years ago most cultures had no reliable method to initiate fire.  It would take humankind another 88 centuries to develop an easy method to start a fire (as in the 19^th century phosphorus friction match) but that is another story.  As humans experimented with the heat of fire they even cooked rocks and dirt – and significantly thereby, created or discovered metals, ceramics and glasses.   Metal, ceramic and glass can be used to manufacture trade items which rank right up there with other achievements (like plant and animal domestication, division of labor and written language) to define what civilization really is.  This half-baked discourse intends to explore some simple metallurgy.

  Smelting is the separation of metal from its ore.  The reduction of aluminum using electrolysis instead of heat can also be called smelting.  Smelting with heat is often assisted by adding a reducing agent and a flux.  When smelting iron, coke or charcoal are added to the crushed ore within a traditional blast furnace and act as a reducer in the redox (reduction-oxidation) reaction.  Carbon monoxide is produced as the oxygen is striped from the iron ore.  Limestone, carbonate of soda, potash and lime might be used as a flux or slag forming agent to absorb impurities into a slag that can be separated from the liquid molten metal.  With the low grade copper ores available today, soap bubbles and pine oils are frequently used as reagents to detach the metal from its crushed ore slurry.  The cyanide process (cyanidation) can be used to extract (smelt) gold, copper, zinc or silver from their low-grade ores.  Mercury dissolves gold and can form amalgams with several other metals as well.  Easily separated from its crushed ore the gold can further be separated from the amalgam (in small samples) by squeezing it through a rag of chamois leather or by baking it in a potato.

  Before turning the discussion to simple blacksmithing some melting points (°F or °C) of some familiar materials are listed in ascending order below.  The temperature of molten lava depends upon its chemical composition.

			number
Tin	449° F	232° C	Sn, #50
Lead	621° F	327° C	Pb, #82
Zinc	787° F	419° C	Pb, #30
Antimony	1,167° F	630.6° C	Sb, #51
Magnesium	1,202° F	650° C	Mg, #12
Aluminum	1,220° F	660° C	Al, #13
lava		800°C
Silver	1,763° F	962° C	Ag, #47
Gold	1,947° F	1,064° C	Au, #79
Copper	1,984° F	1,084° C	Cu, #29
lava		1100° C	basalt
Silicon	2,577° F	1,414° C	Si, #14
Nickel	2,651° F	1,455° C	Ni, #28
glass	2,700° F	1,500° C	soda lime
Iron	2,800° F	1,538° C	Fe, #26
Titanium	3,034° F	1,668° C	Ti, #32
Platinum	3,215° F	1,768° C	Pt, #78
kaolin	3,275° F	1,800° C	porcelain
Vanadium	3,470° F	1,919° C	V, #23
glass	4,200° F	2,300° C	silicon-
Molybdenum	4,753° F	2,623° C	Mo, #42
Tungsten	6,192° F	3,422° C	W, # 74
* Carbon	—	—	C, #6

* Allotropes (forms) of carbon have the highest thermal conductivities of all known materials and they don’t melt.  Carbon undergoes sublimation at about 9,980 °F (5,530 °C) which is to say that the element transitions from a solid to a gas without passing through a liquid phase.  Carbon is also the fourth most common element in the universe by mass, forms more recognizable compounds than any other element and is the chemical basis or building block for all known life. 

In the previous table antimony, vanadium, molybdenum and tungsten are used in small amounts to make alloys and are only included for the sake of curiosity.  Antimony is not a metal but a metalloid.  Like gravel compliments the integrity of concrete, antimony combined with tin, hardens lead for bullets or linotype (the lead alloy historically used for typesetting).  The biggest use for antimony today is in the production of lead acid type automotive batteries and to harden the lead wheel weights used when mounting and balancing new automobile tires.  Vanadium, molybdenum and tungsten serve mainly as steel alloys or as catalysts.  Vanadium is useful in tool steels like drill bits, where it facilitates higher possible working temperatures without sacrificing temper (hardness).  Molybdenum improves steel by restricting its expansion and softening at higher temperatures and was commonly used in artillery pieces and tank armor.  Molybdenum also improves the corrosion resistance and weld-ability of steel.  Tungsten is a rare element but having a very high melting point found use in light bulb and x-ray tube filaments.  Used in cutting tools and abrasives, tungsten –carbide tipped implements are almost three times harder or stiffer than plain steel.  Chromium is yet another metallic element which is often found alloyed within steel.

*  House fires and even forest fires can sometimes reach impressive heats.  Stones in masonry chimneys have been known to explode like bombs when the attached cabin or dilapidated house is burned down.  The pressure probably comes from steam created by moisture trapped within the rocks.  Uniform Building Codes (UBC/IBC) stipulate that steel beams if used to support the roofs of modern wood framed homes and buildings, need to be shielded from possible flame.  Without flame and heat protection steel girders might quickly soften, sag and collapse, leaving potential victims with no exit from the building.  At their flame front wildfires can heat the surrounding air to 1,470 °F (800 °C).  If fed by wind the internal temperature of a wildfire might surpass 2,192°F.  That’s a temperature high enough to substantially soften steel or liquefy several other types of metal.

Cupola Furnace
source: commons.wikimedia.org
Released into the public domain (by the author)

Furnaces

A “bloomery” was the earliest form of furnace capable of smelting iron from ore.   Having a channel for air flow at the bottom the simple bloomery structure was typically sacrificed to retrieve the metal.   Early blacksmiths often worked with iron wrought from a bloom.   A ‘bloom’ (cruder than ‘pig iron’ from a blast furnace) is a porous, impure mass of iron and slag (video links one & two).  The hot bloom was hammered, reheated, pounded, twisted and pulled to squeeze out the slag.  Wrought iron is the almost pure iron product produced by all that excess labor (another video).   Wrought iron is very rare today – its main source being from antique structures or implements.   In its place modern blacksmiths use malleable and ductile low-carbon or mild steels.   Low carbon steel contains about 0.05–0.15% carbon while mild steel is about 0.15 –0.3% carbon.  Further carbon proportions quickly become harder and more brittle.  High carbon steel might contain between 0.6–2.0% carbon.

Although not as old as bloomeries the modern blast furnaces used to smelt ore today are merely embellishments of a design used in the Middle Ages (or since the 1^st century AD in China).   Fed from the top by conveyor belts of ore, coke or coal and limestone (flux) the big chemical reactor called a “blast furnace” works continuously, year after year without being shut off.   It might take an individual atom of iron 8 or 9 days to work its way to the bottom of the furnace.  The name “blast furnace” reflects the fact that air (hot air in modern times) is forced into the bottom.  Crude “pig iron” is the product produced from a blast furnace and this is processed later to become steel.  The “Bessemer process” for economical industrial steel making was patented in 1855 and was the prevalent steel making method for about a century afterward.  The process involved re-melting the pig iron and removing impurities by blowing air through the molten iron.   Following WWII regenerative “open hearth furnaces” began displacing previous Bessemer converters.  Using exhaust gasses to preheat incoming fuel and air, open hearth furnaces operated much more slowly thereby offering more control over the process, allowing the refining of scrap metal along with pig iron and reducing the amount of undesirable nitrogen introduced to the reaction.  By the 1990’s most industrial open hearth furnaces were themselves displaced by the Basic Oxygen Furnace (BOF) and non inductive Electric Arc Furnace (EAF).  The BOF is in essence a refined Bessemer converter where pure oxygen rather than air (which is about 78% nitrogen) is injected into the molten metal.   Perhaps situated next to a blast furnace, the BOF accepts already molten pig iron, mixes in perhaps 20-30% scrap steel and injects oxygen at supersonic velocities.  Great heat is created, the scrap steel is melted and carbon and silicon are oxidized.

Iron ore is basically iron oxide so producing iron metal necessitates removing the oxygen.   This “reduction” is accomplished by using carbon.  At elevated furnace temperatures the strong chemical iron-oxygen bonds in ore are swapped for even stronger carbon-oxygen bonds.  Coke is analogous to charcoal or char cloth and all three are products of “pyrolysis” (the act of driving off volatiles with heat in the absence of oxygen).  Char cloth (from fabric) and charcoal (from wood) are created in an oxygen deficient environment.  Likewise coke is made in a ‘coke oven’ where coal is heated in the absence of air to produce a hard porous material of almost pure carbon which will burn twice as long and produce twice the heat as the original coal.  Coke won’t burn by itself without the forced air or oxygen blast from a blower.  While coke is unanimously preferred over coal for steel making it is also important to make it from coal selected for low sulfur content.  That nasty, odorous and very effective wood preservative used on telephone poles and railroad sleepers is actually a byproduct of the coking process known as coal tar “creosote”.

Blacksmithing 101

Before the appearance of acetylene cutting torches, arc welders, electric drills and saws the principle utilitarian metalworking tools were forges, hammers and anvils.  It is possible occasionally to find portable forges still being used occasionally by cowboys to heat branding irons or by farriers to bend horseshoes.  Forges still have practical applications in this day and age because iron and steel become almost docile and easy to work with when hot.  Looking like backyard charcoal grilles the portable blacksmith forges labeled b & c in the following image probably served in just that capacity on several occasions throughout the last century.

Introduced in the late 1870’s forges resembling images a, b & c replaced the traditional bellows with a geared turbine or blower.  In examples a & b the blower is powered by lever, in example c the geared blower is cranked by hand.  In example d a shop vacuum is used to blow a strong stream of fresh air up through the bottom of the forge.  The concept first published in Popular Mechanics magazine in 1941, example d incorporates a kitchen sink.  One bay of the sink is lined with a cementatious refractory or firebrick while the other can be filled with water for quenching hot metal.  The airflow from the shop-vac or other blower is split between the bottom of the pit and a tube which creates an upward draft in the hood and chimney flue.  A PVC ball valve between the vacuum hose and metal drain pipe adds control to the airflow at the bottom of the forge.

A London pattern anvil
– a design perfected some 300 years ago

Appreciating the many complications of metallurgy takes high science but a rural blacksmith can somewhat refine iron or steel by understanding just a few basics.  By heating metal until it is soft, the blacksmith can easily bend and shape it, cut it, weld it and punch better holes than he can cut with a drill.

The temper of hard steel can be ruined and lost by overheating it.  High-carbon / hard steel must be worked at a lower temperature that mild steel would normally be.  Annealing or softening of carbon steel is accomplished by getting it red hot and then setting off to the side in the ashes to cool slowly.  Annealing might be useful to relieve stresses inside a bent piece of steel before it is to be hardened.  Hardening of carbon steel is accomplished by cooling it quickly – usually by dunking the item in water.  Steel hardened this way can become too brittle sometimes. To temper a piece of steel to a desired compromise between brittle and tough the hardened item is reheated once again – but this time to a lower temperature.

From a microscopic perspective mild steel has a fibrous or stringy structure while hard steel has a fine granular structure.  The blacksmith can distinguish between grades of steel by observing the sparks thrown off when grinding it.  Sparks from mild steel are red or yellowish and fly in straight lines.  Sparks from hard steel are lighter/ brighter in color, sprangled in flight and seem explosive.  The blacksmith develops the ability to judge temperature by observing the color and glow of the underlying heated metal as well as the color of the oxide or scale formed on its surface.  Ranging anywhere between dull red and bright white the glow should be judged in the shade, not in direct sunlight.

Wrought iron or mild steels are forged at yellow heat and using sand as flux between pieces, welded at white heat.  High carbon steels are forged at a lower red to low orange heat and are generally not welded by the blacksmith method.  Overheating tool (hard) steel is likely to destroy the grain structure.  The critical temperature for tool steel is indicated by a dark red color and ranges somewhere between 1,300 and 1,600° F depending upon carbon content.  Heavy hammering a piece of steel upon an anvil at a little above the critical temperature has the effect of reducing the grain size and refining the steel.  The hammering strokes preformed by a blacksmith are not thoughtless or random but are instead precise and calculated.  Light hammer strokes are to be avoided while medium, heavy and extra heavy strokes have their appointed applications.

In addition to a forge and a good heavy anvil that won’t bounce around a blacksmith might have a vise, a pair of tongs, an assortment of cross-peen hammers and a few hardys.  A hardy is an accessory which fits in the hardy hole; it has a square base so it won’t rotate by accident.  Hot metal is cut on the table (or chipping block) which is supposedly made of softer metal than the face – which is made of hard steel and should be kept free of mars and scratches.  Hot chisels are for cutting hot metal and are made of mild steel.  Cold chisels are made of hard steel and should be used for cutting cold metal only.  Holes in hot metal are initiated by punching them upon the face from both sides with a round punch, before being moved over the pritchet hole for completion.

As fuel for the forge the blacksmith can use hardwood, charcoal, coal or coke.  A high quality soft coal free of sulfur is considered the best choice.  Charcoal which comes from wood and coke which comes from coal are both produced by the process of pyrolysis.   Although the volatiles are driven off of the constituents from which they are made, the resulting charcoal and coke have higher carbon contents and therefore make more efficient fuels.  The problem with coke in a blacksmithing furnace is the fact that a steady stream of air from a bellows or fan is needed to maintain its combustion. * Charcoal can be made by digging a hole in the ground, filling the hole with wood and then igniting it.  Once the wood is burning furiously the hole is smothered by sheets of roofing tin perhaps and dirt is spread over that.

The fire in a forge is kept small and tidy, its size proportionate to the work required.  Clinker or slag is removed periodically, fuel added as needed and perhaps water even sprinkled around the rim of the fire to keep the combustion from spreading to an area larger than necessary.  Normally a uniform heat needs to be applied to a piece of metal and so the item is laid horizontally in the fire, not pointed down into it.

__________________________

Note to self: Not only were the redoubtable subjects of ceramics and glass not discussed but important workable metals like bronze & brass deserve honorable mention also.  These subjects need to be attended to in subsequent post…