Leather
the skins of animals chemically modified by tanning and otherwise, so as to arrest that proneness to decomposition which characterizes unprepared skins, and to give to the substance greatly increased strength, toughness, and pliancy, with insolubility and unalterability in water. Remains exist of tanned leather made in Egypt not less than 900 years B. C. There are three methods by which leather is prepared: first, and by far the most important, with tan barks and other vegetable substances containing tannin; second, by tawing with alum, bichromate of potash, and other mineral salts; and third, by shamoying or impregnating the raw skin with oil. The skins of all animals used for leather making consist chiefly of a fibrous gelatigenous substance called collagen, which on being boiled forms the ordinary gelatin of commerce, with an interfibrous compound called coriin, insoluble in water, parts of the world, are a most important source of leather. Goat skins and kid dies, Asia Minor, and Switzerland; but skins come from the Cape, the East Inskins are when imported already tanned, many of the East Indian and Asiatic which have only a local or a limited and require only dressing. Other skins market are the walrus, rhinoceros, and elephant, from which leather of great thickness, suitable for polishing wheels and other mechanical purposes is obtained; and hog or pig skin is an important source of leather for saddle making and other purposes. The skins of various species of deer and antelope, porpoise and kangaroo, are also sources of leather; and from the Cape there are occasionally sent to the London market skins of the gnu and quagga. As sources of leather for fancy articles there may be mentioned the alligator (a leather now extensively imitated), and certain snakes' and sharks' skins.
Tanning. The operations of tanning and the duration of the process vary very widely. Oak tannage is a very tedious process, and the common practice is now to hasten the completion of the operation by mixed tannage, in which more rapidly acting agents play a part.
In the United States hemlock bark from Abies canadensis is the most important tanning material; and the mimosa or but which in common with collagen wattle barks of Australia are very unites with tannin to form the insoluble largely used in the British colonies as and unalterable compound tanno-gelatin, the chemical basis of tanned leather. The skins of all animals may be made into leather; but in practice the raw materials of the manufacturer consist of the skins of certain animals which are reared and slaughtered primarily for other purposes, and of which the supply is sufficiently large to form the basis of a great industry. Large skins, it may be remarked, such as those of oxen and horses, are in trade termed hides; those of calves, sheep, goats, and other smaller creatures are called skins. Of all leather-making hides the most important are those of oxen, which are primarily distinguished as ox, cow, and bull hides, and calf skins. Leading sources of supply are Australia, the Cape of Good Hope, the River Plata and South well as in Great Britain. Standard extracts containing a fixed percentage of tannin have also come into favor for rapid tannage. But, with all the devices which have been suggested, tanning is essentially a slow operation. The great amount of poor leather in the markets is due to hurried preparation and use of chemicals that injure the texture.
In the treatment of ox hides for the production of, say, sole leather, the first object of the tanner is to clean and soften the hide. This is done by washing with water, and if necessary working the hide under stocks till the whole is uniformly soft and pliant. The unhairing and removal of the scarf skin is the next operation, for which in English tanneries the hides are steeped in pits containing lime water, while in the United States the Alpine ch consists pr sheep ski skin of stock sl skin and ing a kind tinous cor liarly soft LEAVE seat of L Missouri z and Santa Chicago, I several oth Kansas C a farming factures machinery wagons, b iron bric brooms.
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LEBAL county se Cleveland Louis and Its indus factories, elevators. (1920) LEBAT the count the Phils wall, and РОДОВ. posits o brick cla industrie brickmak silk, bolts four libr public b (1920) 2 LEPA Syria. つな tains, their logically LEATHER plan adopted consists of sweating the hides, or artificially heating them till incipient putrefactive fermentation is set set up. The hides are afterward stretched over a tanners' beam, and the hair and scarf skin are removed by shaving with a fleshing knife. At the same time the flesh side is gone over, and any fragments of fiber or fat adhering to it are pared away. All traces of lime in the hides must be got rid of, and that sometimes is effected in the first tan pit, containing acid liquors weak in tannin, and LEBANON Alpine chamois. Shamoy leather now consists principally of the flesh splits of sheep skins. The oil is worked by means of stock slowly into the interstices of the skin and there becomes oxidized, forming a kind of combination with the gelatinous constituents, and yielding a peculiarly soft and spongy texture.