Ox gall


Derived from the bile of domestic cows or other bovines, ox gall is added to paint as a surfactant or wetting agent to allow paint to flow more freely.<br><br>A waterless, oil- and water-soluble, translucent, nearly transparent brown liquid, ox gall is the bile taken from the gall bladder of a cow. It is used with watercolors, in engraving, in marbling, and in lithography as a wetting agent ? reducing what&#39;s called the "surface tension" of liquids, improving water&#39;s ability to penetrate and be absorbed. It is also used in the marbling of paper to more smoothly disperse oil color on the size. Ox gall has a long history of use, but often replacing them today are modern synthetic wetting agents available from art supply dealers (photographic and general chemical supply dealers too) in bottle, dropper-bottle, and aerosol forms. Ox gall and other wetting agents are also employed to eliminate pin-holes in gesso surfaces, by mixing it into the gesso before the gesso is applied. Also see absorption, binder, marbling, and medium.