IV.

Deliming and Bating

The next operation involves deliming the skins by soaking them in a weak solution of acid, which reduces the swelling caused by the lime. Simultaneously, most types of skins are treated with a “bating” material consisting of enzymes to give a smoother grain and render the skin soft and flexible. The amount of bating varies greatly, from none at all for sole leather to a concentrated treatment for leather to be used in kidskin gloves. After the deliming and bating operations, the stock can be tanned.

Each type of skin may be treated by several tanning processes. The process is chosen according to the use for which the leather is intended. The two principal tanning processes are mineral, or chrome, tanning, and vegetable tanning. Chrome tanning often can be completed in a single day, whereas vegetable tanning requires many weeks or months. Vegetable tanning results in a firmer leather with greater water and stretch resistance. Chrome tanning shrinks the stock and produces a longer-wearing leather with greater resistance to heat. The processes are sometimes combined to derive some of the advantages of each.