A property of printing inks that describes the extent to which a dried ink film will resist reacting with chemicals with which it comes in contact. Chemical resistance (in particular, the extent to which an ink formulation will resist reacting with acids and alkalis, called alkali resistance) is an important property, especially in packaging. Inks that react with alkalis (such as soaps) will fade, discolor, bleed, etc., when in contact with them, producing undesirable effects when used in the printing of soap packaging. Other chemicals and materials to be packaged must also be compatible with inks used on their wrappers. Chemical resistance is most commonly a property of the ink pigment, and the choice of pigment compound directly affects the ink's resistance to various chemicals. (See Pigment.) Related to chemical resistance is an ink's wettability, which describes the extent to which an ink will resist bleeding, fading, discoloring, etc., upon contact with moisture.
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