It probably did not take long for prehistoric hunters to realize that the skin of their prey was just as useful as its meat. Although an animal's hide would go rancid within a few hours of its death, it could be made into a strong, water-resistant material if properly cured. This process, lengthy and tiresome when done by hand, is today performed by machines. Although it was not until the 1700s that the tanning process was investigated scientifically, the process used today is almost exactly the same process that was developed by tanners thousands years ago.
There are many different kinds of leather. The skin of almost any animal can be cured and tanned--such exotic animals as ostrich, lizard, and eel have been used. However, the majority of leather is obtained from cattle and calf; sheep and lamb; goat and kid; horses and other equines; pig; and shark, seal, and alligator. The type of leather also depends upon the method by which it is tanned. In all cases, the hide is first cured--that is, it is skinned and cleaned, then dried and salted to prevent decay. After the curing process is completed, the hide can be shipped to a tannery.
In ancient times, a tannery probably consisted simply of a group of pits filled with murky solutions of water and oak bark. Other traditional tanners, such as the Eskimos and the Tartans on the steppes of Asia, have long treated (and continue to treat) hides by scraping off the fat and then working it in again with their teeth, thereby retaining the hide's natural suppleness. Still others dipped the skins in vats full of animal urine and excrement.
Modern tanneries use three different methods of tanning, each yielding a different variety of leather. The oldest method, called vegetable tanning, uses many of the same barks, roots, and seeds that were present in ancient tanning pits. Vegetable tanning is a very lengthy process (taking weeks or months) that produces strong leather which resists water; shoes are usually made from this type of leather. In the more specialized tanning method of oil tanning, after the skin has been cured and dried, it is dipped into vats of fish oil and other fats. The hide is then pounded, forcing the oil and fat into the skin; this forces the oils into the hide, where it replaces the water that has been cured out. The result is chamois leather, a very soft material that can be wetted and dried repeatedly without damage. The third method, discovered in 1852 by Swedish chemist Karl Hylte'n-Cavallius, uses mineral salts as the active tanning agent. The method has been improved over the years, making it suitable for practical and industrial use. Since the late 1800's, chrome tanning has been the principal method for tanning leather. This kind of tanning can be completed in a few hours or days. The type of leather produced is soft and pliable, and is an excellent material for gloves, coats, and other clothing, as well as for upholstery and luggage.
The bulk of leather produced today is used in the clothing industry, but leather had far more applications in those ancient cultures that pioneered its use. In addition to clothing, leather was made into ropes, sheaths for knives, harnesses, saddles, and tent coverings. Because it could be treated to resist water, buckets, bottles, and other containers were usually constructed from leather, as were small boats. When made very thin and pliable, leather vellum (parchment) proved an excellent alternative to papyrus and paper as a durable writing surface.
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