The manufacture of leather by Bennett Hugh Garner

Author:Bennett, Hugh Garner
Language: eng
Format: epub, pdf
Tags: Leather industry and trade, Tanning
Publisher: London, Constable
Published: 1920-03-25T05:00:00+00:00

CHAPTEB XVI

THE TANNAGE OF MOROCCOS AND LIGHT LEATHERS

The Tannage of Goat Skins by the vegetable tanning materials, chiefly sumach, yields after dyeing the true morocco leather, of which a great many varieties are manufactured, according to the class of goods for which they are intended.

For high-class work, soft leathers, and fine grain finishes, the bottle (or bag) tannage is used. Each pelt is sewn up all round to form a bag, having the grain side outward and leaving a small opening at the hind shank. The stitching is done by machine or by hand labour, and is afterwards tested by filling the bag with water. A strong infusion of leaf sumach is now made, and the bags nearly filled with this by means of a funnel, and then inflated with air and the hole tied up. The bags in this distended condition are now thrown into a large vat containing a warm, weak sumach liquor, in which they float. They are then kept in constant motion by stirring and pushing into the liquor with poles. After some hours' immersion they are piled on a rack above the vat to drain, and the liquor inside the bags is thereby pressed out by its own weight and the pressure of the piled skins. Occasionally mechanical pressure is also employed. The bags are again filled and the process again gone through, immersing the skins now in a stronger sumach liquor. The stitching is now undone, and the goods washed in paddle and struck out by machine or by hand and dried. By this process the skins are quite effectively tanned in twenty-four hours or less, and a very soft and fine leather results, which, however, is rather open and porous.

For common skins and bolder grains a tannage in paddle is used. A three-paddle system is employed in which a fresh sumach liquor is made up for each pack, and each liquor is used three times. The goods first enter a mellow liquor

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