Post-tanning

Abstract

Post-tanning refers to the wet operations that follow the main or prime tannage: in practice they apply to chromium(III)-tanned leather, but increasingly also to wet white (glutaraldehyde + syntan-tanned) leather. Conventionally, the sequence is retan then dye then fatliquor, each of which might require more than one component. Although these steps involve different reagents, apparently using different chemistries, there are principles in common. The mechanism for fixing a reagent onto the substrate in a heterogeneous reaction, often involving the sulfonate group, is a common thread. A modern approach is to combine two steps, in a so-called ‘compact’ technology.