“tanning” definition

The treatment of the skin with tanning agents to render it durable resilient hard wearing and soft. There are to types of tanning i.e. vegetable and mineral. In the former skins are tanned in pits with plant extracts such as spruce, oak, or alder woods; oak galls, pomegranates or acorn seed husks are used. it is usually the lower part of the shoe that undergo vegetable tanning. In mineral tanning the skins are tanned in drums with alum or chromium salts, the latter shortening the otherwise protracted tanning period to six or seven weeks. It is mainly the upper leather that undergoes mineral tanning.