The adhesion of ink to non-printing areas of a printing plate, which then transfers the ink to undesirable areas of the substrate. In waterless printing, a variety of offset lithography utilizing a silicone compound rather than water as a means of repelling ink from non-image plate areas, the plates are very temperature-sensitive, and increases in ink temperature cause the silicone compounds to lose their ink-repellent properties, resulting in accumulation of an ink film in undesired areas. Toning is also known as scumming.