Fatliquors

Fatliquors are lubricants used in leather processing to soften and lubricate the collagen fibers of hides during tanning and retanning. They are applied as emulsions that penetrate the treated hide, imparting flexibility, reducing stiffness, and improving the leather’s hand and drape.

Most fatliquors are oil-in-water emulsions containing natural or synthetic oils (such as animal fats, vegetable oils, or mineral oils) stabilized by surfactants. Some modern formulations include silicone or polymeric lubricants to enhance softness, water repellency, or the appearance of the finished leather. Fatliquors are often categorized into penetrating (internal) types that migrate into the fiber to lubricate from within, and surface or partially penetrating types used to modify the surface feel and appearance.

Mechanism and effects: by occupying interfibrillar spaces and reducing friction between collagen fibers, fatliquors increase flexibility and reduce shrinkage, brittleness, and tendency to crack. They influence the leather’s softness, stretch, and fullness, and can affect dye uptake and the final color. If overused, they may cause a greasy hand, alter grain tightness, or impact finishing adhesion.

Application: fatliquors are typically introduced during tanning or retanning steps, often during the bath or bath retanning, and may be followed by drying and dyeing. Selection depends on desired softness, texture, and end-use of the leather.

Safety and environment: formulations are engineered to balance performance with safety and environmental considerations. Fatliquor effluents contribute to wastewater treatment challenges and require appropriate controls in industrial settings.