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 ABOUT LEATHER |
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GENUINE LEATHER . . . words that conjure up imagery and fantasies: “King of Fabrics — Mark of Luxury” — the unmistakable smell, the suppleness, the strength, the sensuousness, stiffness, brittleness, cracking, wearing, unsightliness — the need to reupholster! That’s leather! But, even with all of these impending deterioration processes, genuine leather cannot be imitated and has no substitute. Predating recorded history, cavemen were running around clubbing animals and covering themselves with the skins. It is not certain how the “tanning” process actually began, but we do know that generally, the same techniques used then are still used today — thousands of years later.
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| In the Boston Art Museum there is a beautiful coat of white antelope that was made in Egypt about 3000 B.C. Scholars have learned from tomb paintings that tannin liquors were used by the Egyptian craftsmen to transform animal skins into leather. Other methods were used by the ancients to process and preserve skins and hides. They include the use of grease or oil, minerals, alum and even smoke. But that 5,000-year-old vegetable tannin method, at least in principle, is used to this day. It is based on the fact that tannin, a bitter ingredient found in vegetation, will combine with the proteins of the skin, forming a chemical compound that resists decay. Hemlock and oak liquors and extracts are used more than any other tanning preparations. |
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| During the Middle Ages workers in leather formed powerful trade guilds, and the craftsmen produced many useful and ornamental articles. Since the equipment required was relatively simple, tanning was essentially a home industry and methods of preparing leather changed little for centuries. Toward the end of the 18th century, however, the Industrial Revolution brought about great changes. Ingenious machines were invented and new techniques were developed; large factories gradually replaced small establishments. |
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| Today leather is an important industrial material. Yet, curiously enough, it is a byproduct of another important industry — meat packing — because most leather is derived from the skins of animals such as cattle and sheep that are used for food. |
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Because the ancient vegetable tanning method is so time consuming (it takes several months), modern tanners use chromium salts to produce the same results in less than 24 hours. This chrome tanning method was known as early as 1856, but it was not practical until it was perfected by the American inventor August
Schultz in 1884. |
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| To prepare the skins for tanning, they are sprinkled with salt or immersed in brine within a short time after the animals are killed. This process preserves the skins by partially dehydrating them and by killing certain bacteria. The salting process, however, does not preserve the skins indefinitely, so they are tied into bundles and shipped to the tanneries. |
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| The tanner begins by cleaning the skins thoroughly. They are put in soaking vats of cold, clean water for from one to seven days, so that the salt is dissolved, the dirt is loosened and the skin is restored to a soft condition. |
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| Next, to remove the hair, the skins are again placed into vats, this time containing chemicals to loosen the outer layer of skin in which the roots are embedded so that the hair may be easily removed. |
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| From two to seven days later the skins are fed into the “unhairing machine,” which is similar in construction to the fleshing machine except the knife edges are dull. The squeezing action of the dull knives removes practically all the hair and its roots. Any hair remaining is pulled out by hand. |
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| In order to remove the chemicals used in the unhairing process, the skins are subjected to yet another bath called the “bating bath,” containing an extract of pancreatic glands and an ammonia compound. This also dissolves certain proteins, making the skin soft and pliable. |
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