Leather

the skin of an animal dressed by a process called tanning. The skins of the cow, ox, buffalo, elephant, and other large, thick-skinned animals are called hides, as distinguished from the skins of calves, sheep, goats, dogs, and fur-bearing animals. Kip leather is produced from the hide of a half-grown animal. Green hides are rubbed with salt to prevent putrefaction, or else they are dried before they are sent to market. Both green hides and dried hides may be converted into glue by boiling. So far as the art of tanning is concerned, all skins and hides consist of three layers,--the outer or epidermis, including the hair; an inside fleshy, fatty layer; and a third, or intermediate layer between the two, out of which leather is made. The preparation of leather consists of two entirely distinct processes. First, getting rid of the hair and the flesh; second, filling the central layer with curative and preservative material. Skins valued for their fur are, of course, dressed and tanned from the flesh side only.

There are many ways of removing the hair and fat. One of the simplest consists of laying the hides in a bath of milky limewater for from two to twenty days, which loosens the epidermis and hair, and forms a kind of soap with the fatty matter. During this process the hides are turned over frequently and are churned about to make sure that the lime reaches all parts. Working or handling, as it is called, also assists in breaking up the epidermis and fatty cells. When taken out of the lime bath, the hides are scraped both inside and out with knives until nothing is left but the fibrous portion of the hide. The skins are now ready for the real process of tanning which converts them into leather. This may be done by immersion in a vat containing liquor strongly impregnated with tannin,--a strong coffee-like liquid obtained from the ground bark of oak, hemlock, birch, beech, or from the leaves and shoots of the sumac. The wood of a tree found in Argentina yields a fourth of its own weight of tannin. The more the hides are handled during this process, the more flexible and soft the leather. This treatment is continued for from one to six weeks, and then the hides are shifted into a second vat containing a still stronger decoction of tannin. To obtain the best results, the tanning process should continue for eight or ten months. After this the skins are worked thoroughly over a beam, and are shaved carefully on the flesh side to a uniform thickness. They are then filled with a mixture of oil, soap, and tallow, thoroughly worked in by a prolonged tumbling about in a revolving drum. There are shorter methods, but they do not produce as durable leather.

Leathers intended for the uppers of boots and shoes are blackened on the hair surface with a mixture of lampblack and oil or tallow. The treatment of sole leather, intended for the soles of boots and shoes and similar purposes, is more simple, as a less degree of flexibility is desired. In place of tannin from vegetables, a tanning solution is made of certain minerals compounded of alum, salt, sulphur and other elements. Well tanned leather is flexible, soft, tough, and proof against all forms of bacteria; that is to say, it will not putrefy under any circumstances. Leather exposed to moisture, however, especially in a dark place, will mold.

Tanning is at bottom any process that renders the fiber proof against the attacks of bacteria; that is to say, against putrefaction. This may be accomplished also by a process called oil tanning. Oil-tanned leather is leather in which the tanning bath is omitted. The skins are pounded, rolled, and pressed in oil until every particle of animal matter capable of putrefaction has been driven out and replaced by preservative oils, chiefly those of the whale or cod. The Indians tanned their buckskins by filling them with the oily brains of the deer.

Chamois leather is tanned in oil. Morocco leather is tanned with sumac and stained with dye. Patent leather is made by splitting a skin into thin layers and coating them with a varnish of linseed oil containing lampblack and some other coloring matter, as Prussian blue. Parchment is made from the skin of sheep from which the flesh and hair have been removed in the usual manner. It is then stretched on a frame, and putrefying matter which it contains is absorbed by powdered chalk, after which the surface is smoothed with pumice and scraped with a steel blade. The skin is then dried and smoothed into shape. Vellum is made in a similar manner. The making of leather is an ancient art preceding the dawn of history. The Egyptians tanned leather certainly 3,000 years ago.

The United States leads the world in the production of leather. 600 tanneries produce one-fourth of the world's supply. Every year nearly 200,000,000 hides and skins pass through these 600 tanneries, and when finished into leather they are worth $250,000,000. It requires 1,250,000 cords of tanbark and 650,000 barrels of extract to meet the demands of the American tanner in the conversion of these hides and skins into leather. Two-thirds of the tanbark used is from the hemlock tree. Philadelphia is noted for the production of kid leather from the skin of the goat and substitutes. A quarter of a millon alligator hides are said to be tanned yearly at Newark, New Jersey.

See Buckskin; Morocco; Boots And Shoes; Gloves; Pergamus