A property of printing inks that describes the extent to which a dried ink film will resist fading, discoloring, deterioration, and bleeding when in contact with soaps, an obviously important consideration in the printing of soap packaging. Other chemicals and materials to be packaged must also be compatible with inks used on their wrappers. Soap (and other chemical) resistance is most commonly a property of the ink pigment, and the choice of pigment compound directly affects the ink's resistance to soaps and other alkalis. (See Pigment.) (See also Chemical Resistance and Wettability.)
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