On Tanning Leather. - Preparation of Hides.

Scientific American 22, 16.2.1850

For the Scientific American.

(Continued from page 168.)

Tawing, Currying and Leather Dressing

Saffian Leather.
A valuable Saffian or dyed Maroquin leather, almost equal to that of Turkey, is prepared Astrancan, and in other parts of Asiatic Russia. Buck and goat skins are the only ones used for this purpose, and the favourite colours are red and yellow. The general method of preparing the pelt is the same as used in this Country for the dyed Morocco leather: that is, by lime, dog's dung, and bran. Honey also is used after the branning; it is dissolved in warm water, and some of the liquor poured on each skin, spread out on wooden trays, till it has imbibed the whole of the hoey after which it is permitted to ferment for about three days, and then salted in a strong brine and hung up to dry. The skin is then ready to receive the dye, which for red is made with cochineal and the Salsola ericoides, and alkaline plant growing plentifully on the Tartarian salt deserts, and the colour is finished with alum. When dried, the skins are generally tanned with sumach, but for the very finest reds a quantity of sorrel is used with the cochineal bath, and the subsequent tanning is given with galls instead of sumach, which render the colour as durable as the leather itself. The roughness always observed on the surface of the skin is given by a heavy kind of iron rake with blunt points. The yellow Saffians are dyed with the berries of a species of rhamnus, (the Avignon berry would answer the same purpose, and is used in other Countries,) or with the flowers of the wild camomile.

Shagreen Leather.
This singular and valuable leather is a manufacture almost peculiar to Astracan, where it is prepared by the Tartarsand Armenians. For making shagreen only horses' or asses' hides are taken: and it is only a small part, from the crupper along the back, that can be usef for this purpose, which is cut off immediatelly above the tail in a semicircular from, about 34 inches upon the crupper, and 28 along the back. These pieces are first soaked in water till the hair is loose and can be scraped off, and the skin, after being again soaked, is scraped so thin as not to exceed a wetted hog's bladder in thickness, and till all the extraneous matter is got out, and only a clean membraneous pelt remains. The piece is then stretched tight on a frame, and kept occasionally wetted, that no part may skrink unequally. The frames are then laid on a floor with the flesh side of the skin undermost, and the grain side is strewed over with the smooth black hard seeds of the Ala lenta or goose foot, and a felt is then laid upon them, and the seed trodden deeply into the soft moist skin, which gives the peculiar mottled surface for which shagreen is distinguished. The frames, with the seed still sticking to the skin, are then dried slowly in the shade, till the seeds will shake off without any violence, and the skin is left a hard horny substance with the grain side deeply indented. It is then laid on a solid block covered with wool, and strongly rasped with two or three iron isntruments, till the whole of the grain side is shaved, so that the impression of the seeds is very slight and uniform: the skins are then softened first with water and then with a warm alkaline ley, and are heaped warm and wet on each other, by which means the parts intented by the impression regain much of their elasticity, and, having lost none of their substance by paring, rise up fully to the level of the shaved places, and thus form the grain or granular texture peculiar to the shagreen. The skin is then salted and dyed.

The beautiful colour is given by soaking the inner or flesh side of the akin with a staturated solution of sal ammoniac, streqing it over with copper filings, rolling it up with the flesh side inwards, and pressing each skin with a considerable weight for about 24 hours, in which time the sal ammoniac absorbs enough of the copper to penetrate the skin with an equable sea-green color. This is repeated a second time to give the color more body. Blue shagreen is dyed with indigo, dissolved in an impure soda by means of lime and honey.

Black shagreen is dyed with galls and vitriol: they are in each case finished with oil or suet.