Technical Abstract: Thirty million pounds per year of fats and oils are used in the leather industry. Most is used in the leather to soften it. Softening occurs by break-up of thick fibers or by preventing them from forming when the leather is dried. The fat is usually added as an aqueous emulsion. The emusifier is selected for its ability to break when in the presence of the leather fiber surfaces and the chromium-oxide tanning agent. Fats and oils that are used include triglycerides, mineral oil, wool grease, partially sulfonated cod oil, neatsfoot oil (from bones), linseed oil, rapeseed oil, soy oil, coconut oil, and rice-bran oil. The minimum chain length for a fat molecule is 18 carbon atoms. New developments are polymers based on long-chain fatty acids.