Fatliquoring

Fatliquoring is a conventional step in leather processing in which lubricating fats or oils are introduced into the collagen fibers of a tanned hide or skin. The aim is to impart softness, flexibility, and drape, while controlling dryness and shrinkage. Proper fatliquoring results in a uniform hand and improves dye penetration and overall appearance.

Fatliquors are typically emulsions of fats or oils (natural, animal, vegetable, or synthetic) with surfactants and stabilizers. They are applied to the wet leather by padding, immersion, spraying, or vacuum-assisted pumping in the wet-end of the tannery. The emulsified lipids diffuse into the interfibrillar spaces of the collagen, lubricating the fibers and reducing internal friction.

Outcomes include increased pliability, reduced stiffness, and improved resistance to cracking. It also helps to regulate moisture uptake and can influence the leather's finish and color uniformity. Excessive fatliquor or poor emulsion stability can cause oil bleed, diminished dye uptake, or a greasy surface, and can reduce tensile properties if mismanaged.

Variations exist for different leather types (aniline, nubuck, suede) and tannages (chrome, vegetable). Environmental and safety considerations are important, as some fatliquors can contribute to effluent load; modern formulations emphasize lower residue, higher bio-derived content, and compatibility with finishing systems.