A substance added to a printing ink to prevent ink setoff, the undesirable transfer of ink from a printed sheet to the back of the sheet lying on top of it in the delivery pile. Anti-setoff compounds—commonly starch or silica powders—typically reduce this problem either by forming a protective layer on the surface of the ink film (their particle size is greater than the thickness of the ink film, allowing them to protrude through the surface of the film, keeping the adjacent sheet physically separated from the wet ink), or by expediting the drying time of the ink. Anti-setoff compounds are favored over anti-setoff sprays. See also Anti-Setoff Spray.
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