LEATHER – 1
Post 235 ⇒ by Gautam Shah →
Leather has been used by primitive man to cover own-self, protect food items, carry water, form a place of dwelling, to tie materials and make footwear. Raw hides or untreated skins have a tendency to putrefy very quickly in wet weather, causing foul smell and degeneration of the material itself. In dry conditions, or on loss of moisture untreated skins become very hard, rigid and brittle.
Leather processing is an ancient craft that has been practised for more than 7,000 years. The first lessons were how to turn rawhides in to a stable product, Leather. For leather making rawhides must be removed early, cleaned, washed and dried in the sun. There were two easy treatments for making leather, better lasting, soft and a wearable product. The first was to curtail leather’s reactivity with moisture by coating it with oils or wax. Other methods included, salting (to dehydrate) and smoking to retard bacterial activity, and treatment with bark extracts (for tannic acid), and alum.
The hides of mammals, the chief sources of leathers, are composed of three layers: epidermis, a thin outer layer, corium, or dermis, the thick central layer, and a subcutaneous fatty layer.
The corium constitutes the main commercial leather, after the two sandwiching layers have been removed. Fresh hides contain between 60 and 70 percent waters by weight and 30 to 35 percent protein. About 85 percent of the protein is collagen, a fibrous protein held together by chemical bonds. Basically, leather making is the science of using acids, bases, salts, enzymes, and tannin to dissolve fats and non-fibrous proteins and strengthen the bonds between the collagen fibres.
The term hide is used to designate skins of larger animals, e.g. cowhide or horse-hide, whereas skin refers to smaller animals (calfskin or kidskin). Fur is a hide or skin of furry or hairy animals. Use of furs precedes use of hides as several species of hominoids including Homo sapiens and Homo neanderthalensis used fur for clothing. Common animal sources for fur include fox, rabbit, mink, beaver, stoat (ermine), otter, sable, seals, cats, dogs, coyotes, chinchilla, and possum. Major sources of leather were hunted animals, but later domesticated cattle and skins of calves, goats, kids, sheep, and lambs, were used. Other sources were horse, mule, pig, kangaroo, zebra, deer, seal, walrus, and reptiles. Skins of ostrich, lizard, eel, and of aquatic creatures such as seal, walrus, whale, and alligator were used.
Leather cleaning included scrapping the back or underside of all residual tissues, blood, etc. and top side of hair or wool by stone or wooden scrapers. The processes for tanning of leathers were developed at many places, in stone age period. Tanning could take up two years for very thick hides. The dressing of leather involved paring or shaving it to achieve a level thickness. Leathers were surface treated with wax, oils and dissolved gums, often with colourants.
Sumerians in Mesopotamia, during the 5th and 3rd C. BC. used skins for long dresses and diadems for ladies. Egyptians also used leather for clothing including gloves arms, belts and as ornaments. Phoenicians are credited with forming water tubes of leather. Romans and many other in central Asia were using leather footwear, clothing, shields and riding gears such as harnesses. Assyrians used leather for containing oils, and as inflated floats for rafts. In India thinned raw-hides were used as cover for percussion instruments.
By 1st C Ad a vast variety of hides and skins were produced, many with unique characteristics due to local materials and protected knowledge base. Leathers for parchment or writing media were extremely thinned down and stabilised from raw hides. Skins used for gloves and footwear toppers were soft and supple. Patterned skins of reptiles formed pieces of ornaments. Leather stripes, entwined leather belts, were used for their flexibility and tensile strength. Furs, were prized items for wearing, furnishings and arms covers.