Principal basic fatliquoring substances

The degree of purity of the oils should be observed. Filtered or refined products are suitable. Heavy impurities cause odour problems. Products of high iodine value (except for chamois tannage) have a tendency to effect intensive yellowing of the leather and quick oxidation.When using neatsfoot oil, cold-resistant products should be chosen. Lard oil should not have solid constituents either as otherwise
there is a risk of fatty spew. All products have an increased content of stearic fatty acid and thus a very strong tendency to form fatty spew. The use of raw materials which have been stored for some time should be avoided because of the rancid smell.Only refined products should be used as this category of products is prone to rancidity which may cause disagreeable smells. Only scmi-drying and non-drying oils are suitable for fat liquoring of leathers. Some products have a tendency to oxidation and thus to develop strong,
 disagreeable smells. Wool grease (lanolin) should be used in purified form because products of inferior quality have a disagreeable smell. Products based on wool grease reduce the wetting properties of the leather.
Paraffin oils only have an adequate fatliquoring effect from a medium chain length of C 20.
Mineral oils should be Iight-coloured, odourless, and the viscosity should not be too low. Furthermore they should have only a low content of aromatic hydrocarbons as othenvise increased yellowing may occur.

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