There is also a process of unhairing, called “sweating,” which softens the hide and loosens the hair so that it can be scraped off. In this process the hides begin to decay before the hair is loose; it is therefore a dangerous process to use and must be carefully watched or the hides will be entirely spoiled. Sweating is never used for the finer, softer kinds of leather. It is applied chiefly to dry hides for sole, lace, and belt leather. It is an old-fashioned process and is not used as much nowadays as some years ago.
The pelts of sheep are salted at the slaughterhouses and then shipped to the tannery. Here they are thrown into water and left to soak twenty-four hours to loosen the dirt and dissolve the salt. The pelts are next passed through machines that clean the wool, and any particles of flesh remaining on the inner or flesh side are removed. The pelts are then in condition to have the wool removed. As long as a sheepskin has the wool upon it, it is called a pelt; as soon as the wool has been taken off, it is called a skin or a “slat.”
Each pelt is spread out smoothly on a table with the wool down and the inner or flesh side up. A mixture of lime and sulphide of sodium is next applied uniformly over the skin with a brush. The pelt is then folded up and placed in a pile with others. The solution that was applied penetrates the skin and loosens the wool, which, at the end of twenty-four hours, more or less, can be easily pulled off with the hands or rubbed off with a dull instrument or stick. The workman must be careful not to get any of the solution on to the wool, as it dissolves it and makes it worthless. Since the wool is valuable, the solution must be applied to the flesh side very carefully so that it does no injury. The wool that is removed from the skins is called “pulled wool.”
The slat is now ready to be limed, washed, pickled, and tanned. Heavy skins are often split into two sheets after they have been limed. The part from the wool side is called a skiver, and that from the flesh side is called a flesher.
After the skins have been limed, they are bated and washed, which makes them soft, clean, and white; they are then put into a solution of salt, sulphuric acid, and water, called “pickle,” and after a few hours they are taken out, drained, and tanned.
Large quantities of sheepskins are sold to tanners in the pickled condition by those who make a business of preparing such skins and selling the wool. Pickled skins can be kept an indefinite length of time without spoiling; they can also be dried and worked out into a cheap white leather without any further tanning whatever. Most of such skins, however, are sold to tanners, who tan them into leather. Sheepskins contain considerable grease, which must be removed before the leather can be sold.
For some processes of tanning, calfskins, goatskins, and cattle hides are also pickled the same as sheepskins; for other processes they are not pickled, but are thoroughly bated or delimed, washed, and cleansed. Heavy hides are sometimes split out of the lime; more frequently, however, they are not split until after they have been tanned.
To capitulate, the preparatory processes may be briefly described as follows:—
Soaking, which dissolves the salt, removes the dirt and makes the hides soft and comparatively clean.