Neatsfoot oil is a yellow oil rendered and purified from the feet (but not the hooves) and shin bones of cattle. It remains liquid down to a low temperature, and is used as a conditioning, softening and preservative agent for leather. In the 18th century, it was also used medically as a topical application for dry scaly skin conditions.
Neatsfoot oil remains liquid at room temperature because the fat in animals' legs generally has a lower melting point than the body fat. This occurs because the legs and feet of such animals are adapted to tolerate and maintain much lower temperatures than those of the body core, using countercurrent heat exchange between arterial and venous blood. Because of this, neatsfoot oil remains liquid at room temperature and so can easily soak into leather.
Currently, neatsfoot oil is sometimes made from lard.^[1] It is sold as neatsfoot oil in pure form, or neatsfoot oil compound, if mineral oil is added. Some brands have been shown to be adulterated with rapeseed oil, soya oil, and drying oil^[2]. Pure neatsfoot oil comes in two forms: regular and cold tested. In the latter, the oil is filtered at 0 to -4°C to remove solid components, as they can lead to 'spewing' (a whitish crystalline deposit or bloom resulting from fat migration).^[3]
'Neat' in the oil's name comes from an old term for cattle, and even today the best quality neatsfoot oil still comes from the legs of calves and with no mineral oil added. "Prime neatsfoot oil" or "neatsfoot oil compound" are terms used for a blend of pure neatsfoot oil and non-organic oils, generally mineral oil. Although the "Prime" is marketed as "the saddlemaker's choice", many saddle makers actually recommend pure neatsfoot oil for leather goods, particularly saddles. Pure neatsfoot oil has superior softening and preservative properties, the addition of mineral oils often leads to more rapid decay of stitching and speeds breakdown of any adhesive materials that may have been used.

Neatsfoot oil, like other leather dressings, should not be used on important historical objects, as it will oxidize with time, and embrittle the leather even more.^[4] It also may leave an oily residue that can attract dust. On newer leather, it will inevitably darken the leather, even after a single application, and thus is not a desirable product to use when maintaining a lighter shade is desired. However, for routine use on working equipment, particularly in dry climates, it is a powerful softening and conditioning agent that few modern synthetic alternatives can replace.

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