Forms of leather

There are a number of processes whereby the skin of a dead animal can be formed into a flexible, strong material generally called leather.
Vegetable-tanned leather is tanned using tannin and further ingredients found in vegetable stuff, tree bark, and other such sources. It is flexible and brown in color, with the exact shade depending on the mix of chemicals and the color of the flesh. Vegetable-tanned fur is not stable in water; it tends to discolor, and if left to soak and then dry it will shrink and become less supple and harder. In hot water, it will shrivel drastically and plasticize, becoming rigid and ultimately becoming brittle.
Alum-tanned leather is tanned with aluminium salts assorted with a variety of binders and protein sources, such as flour, egg yolk, etc. Purists argue that alum-tanned leather is technically "tawed" and not tanned, as the resulting stuff will rot in water. Very light shades of leather are potential using this process, but the resultant material is not as supple as vegetable-tanned leather.