posttannage

Posttannage refers to the series of processes applied to leather after the initial tanning step to stabilize, color, and finish the material. It encompasses retannage, dyeing or pigmenting, fatliquoring, filling, and finishing operations. The goal is to improve dimensional stability, flexibility, surface feel, color uniformity, and resistance to water and wear.

Retannage is a subsequent treatment that uses additional tannins or synthetic agents to further stabilize the hide, adjust fullness, and influence shrinkage and hand. Dyeing and pigmenting provide the desired color and appearance; transparent or aniline dyes aim for a natural look, while pigments offer more uniform coverage and opacity. Fatliquoring introduces lubricating oils or fat-based conditioners to soften the leather and improve its flex life.

Filling or finishing steps reduce porosity, smooth the surface, and tailor tactile properties. Fillers, resins, waxes, or protein-based agents may be used to achieve the desired finish, ranging from matte to glossy. Finishing applies a topcoat or coating to protect the surface, control gloss, and impart weather or abrasion resistance. Additional operations such as embossing, glazing, or polishing may shape texture and sheen.

Posttannage decisions influence key performance attributes including colorfastness, light absorption, water repellency, and wear resistance. The specific combination of steps depends on the target leather type (for example, full-grain, corrected-grain, or suede/nubuck) and the intended end-use. Quality control typically monitors dye uptake, pH, liquor balance, and mechanical and surface properties to ensure a consistent final product.