Crust Leather which has been tanned but not finished. Such leathers referred to as being "in the crust."
Leather that has been through the tanning process, aniline dyed, milled and dried, but with no surface finish at all.
Rarely used for furniture as it is so sensitive and impossible to clean or repair without leaving evidence

Once the skins have been dried, they are taken to the Crust Warehouse for sorting.
The name crust coming from the fact the skins are very hard at this time having only had a basic tannage and minimal oiling.
It is worth noting at this stage that skins are often bought or sold in the crust.
This happens with many different types of skin from all over the world, but especially in the case of skins from the tropical areas of the world.
The reason for this is that in hot humid climates, tanning the leather is the safest method of preserving the skins from rotting.
In the case of bookbinding leathers, the two main sources of goatskins come from India and Nigeria, and are both sold in the crust state.
Whilst this does give that advantage of skins generally free from the problems of putrefaction, the buyer is limited in the type of tannage offered, and therefore in the end product that can be produced.
Alum tawed goatskins, for instance, cannot be produced from vegetable tanned crust leather as this is a specific tannage in its own right.