13 ноября, 2015 
Pokraskin Pigments such as white lead and zinc oxide react with free acids in paints and coatings to respectively form lead and zinc soaps of the acids. Titanium dioxide and many other extender pigments are non-reactive and do not form soaps. Lead and zinc soaps have low solubility in the vehicle and tend to increase the consistency of the paint. They also tend to prevent hard settling of pigment in the paint can during storage.
Pigments that have very small particle size, such as carbon black, iron blue, and certain organic pigments, may produce a physical or colloidal reaction in paint. The reaction results in an increase in consistency, which may become so great that an irreversible sol-gel transformation occurs and the paint becomes similar in texture to liver of human body. The phenomenon is referred to as livering, but the mechanism is not well understood. Apparently, pigment-vehi-
cle complexes are formed that associate to produce a gel structure throughout the paint. In some cases, the pigment particles appear to form complexes with a near-gel fraction of the binder; in other cases, the pigment strongly adsorbs some of the solvent. Care must be taken to avoid livering because its irreversible character makes the paint almost impossible to apply satisfactorily.
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