Crust leather

Crust leather is the term applied to leather, which is dried after tanning but has not yet been dyed. In the case of chrome-tanned leather, this is known as “Chrome crust” and, for vegetable-tanned leather, as “Vegetable crust“.Crust leather is rarely processed as it is. Usually, the leather is dyed and finished before processing.

Crusting is part of the steps for leather production. The main stages of the leather production process are called, preparatory stages, tanning, crusting and surface coating.
chiefessays.net theessayclub.com
Crusting is when the hide is thinned, re-tanned and re-greased. Often a dye process is included in the crusting. Also, part of the crusting process involves drying and softening.