The first three of these stages are to prepare the hide for tannage.
Initially the delime reduces the pH and in doing so reduces the swollen
nature of the hide, this is done both by washing and chemical additions.
Following the delime bating is carried, this removes the unnecessary
interfibrillary proteins by the careful use of enzymes, this gives rise to
a softer more stretchy hide. After bating is completed the temperature of the
hides is reduced by washing in cold water this also removes the dirt from the bating
For the pickling, salt is added to inhibit swelling which could occur
when the pH of the hide is further reduced by addition of acid, this then
promotes the penetration of the chrome tanning. For the limesplit hides
electrolyte stable fat liquors can be added to give an improved softness.
The tannage is carried out using Chromium III Sulphate (33% basic). As the
process progresses the pH is gradually raised causing the chrome to attach to
the hide fibres, by the end of the process the resultant leather good thermal stability properties.