17: Fatliquoring

The fatliquoring or lubricating step in leather making has the primary purpose of preventing the fibre structure from sticking during drying after completing the wet processing steps: the secondary effect is to confer softness. Effective lubrication ensures the leather can exhibit the maximum strength allowed by the processing and the material. Lubrication is typically achieved through the self-emulsifying properties of oils, natural or synthetic, which have been partially sulfated or sulfited: the ‘sulfo’ fraction is the emulsifier carrier in aqueous solution of the neutral oil, which is the active agent in the lubricating mechanism. A complementary process is to confer water resistance to leather: traditional and recent methods gave results that were erratic at best, but modern chemistries, based on partially esterified acrylate polymers and/or silicones, are effective and consistent – if the rules of processing are not broken.