fatliquor

Fatliquor refers to lubricating agents used in leather processing to soften and improve the flexibility of leather. It is typically applied during tanning, retanning, or post-tanning stages to lubricate collagen fibers, reducing stiffness and enhancing the tensile feel and handle of the finished product. Proper fatliquoring helps even dye uptake and can contribute to a more uniform surface appearance.

Composition and mechanism

Fatliquors are usually oil-in-water emulsions. The base oil can be animal fats, vegetable oils, mineral oils, or synthetic esters, often combined with emulsifiers, stabilizers, antioxidants, and preservatives. When applied, the fatliquor penetrates the leather, coating and lubricating the fibrils inside the grain layer. This lubrication lowers internal friction, improves pliability, and can influence the leather’s workability during cutting and sewing. In some formulations, fatliquors also enhance uniformity of color and, to a lesser extent, water repellency and surface appearance.

Application and process

Fatliquoring is commonly performed after tanning and neutralization, sometimes during a secondary retannage. It can be carried out in drums, by padding, spraying, or immersion, depending on equipment and the desired effect. The dosage and choice of fatliquor depend on the type of leather (full-grain, corrected grain, nubuck, suede), end-use requirements, and compatibility with other finishing steps. Proper formulation and application are important to avoid issues such as color migration, uneven softness, or residue on the surface.

Types and considerations

Fatliquors vary in pH stability and reactivity, with neutral, acidic, or reactive formulations available. They must be compatible with tanning systems, stable to heat and oxidation, and non-yellowing. Modern formulations often emphasize low environmental impact and skin-friendliness, including vegetable-based or low-VOC options.