Migration

Part 6 - Leather

As they migrated north our ancestors hunted wild animals for food and, as the climate got cooler, they used the inedible fur covered skins for clothing, crude tents and footwear. If they cut around a deer legs in two places they could roll off tubes of skin that would serve as leggings or, if they tied a knot at one end of the tube, boots. When these were stuffed with dry grass, they were serviceable through the winter.

The furs worked during cold winters but the raw hides dried out into a hard, stiff material that, rotted when it became wet; then it began to stink and usually the fur fell out. People discovered that by meticulously scraping off any flesh and fat from the skin (or hide) and keeping it dry, they could postpone the decay.  After many trial and error experiments they discovered that removing all flesh and hair and soaking the raw skin in a 'soup' of plant materials that contained tannic acid, like oak tree bark, hemlock bark or sumac leaves, they could make a durable leather. This proved to be invaluable for gloves, sandals, boots, tents, capes, hats, carrying bags, water bottles, belts and slings.

The history of leather began about 400,000 years ago but records date from wall paintings in Egyptian tombs from 5000 BCE and Greek records from 500 BCE describing vegetable tanned leather as a well-established trade.

Leather working was a major industry in ancient Rome, mainly to supply the army. Horses required saddles, reins and straps and soldiers needed belts, sandals, boots, sword scabbards, arrow quivers and shields. Helmets and hard, tough armour were also shaped from leather. The Romans also mixed alum (aluminum oxide) with protein binders such as flour and egg yolk,in a process called "tawing" that produced a softer leather but this would revert to rawhide if soaked in water long enough to remove the alum salt.

Early tanners prepared skins, by soaking them in water to clean and soften them, before scraping and beating the skin to remove flesh. They removed hair by soaking the skin in urine, coating it with an alkaline lime mixture, or by letting the skin rot for several months before soaking it in a salt solution. They softened the skin by 'bating' it; soaking it in a solution of animal brains or excrement (dung) and allowing it to ferment as enzymes and bacteria in the dung consumed remaining flesh.

Finally, tanning began typically by soaking the prepared hide in a solution (liquor) containing oak bark, (or other vegetation containing tannic acid), to stabilize the collagen proteins of the raw hide. The skin was then stretched on a frame, so that it lost moisture and absorbed the tanning compound, and was then typically oiled to increase water resistance.

Vegetable-tanned leather left to soak in water and then dried, shrank and became harder which was useful for shoemaking. In hot water or boiling wax, it shrank and became rigid which made it useful for armour.

Parchment was a thin hard leather used for writing, as a more durable material than papyrus, before the invention of paper.