A printing ink defect in which substances from the interior of an ink film rise to the surface, producing a distortion or discoloration of the ink film, commonly caused by too-rapid evaporation of ink solvent. Bloom caused by solid materials is commonly referred to as exudation. (See also Blushing.)
The term bloom is also used to refer to the desirable rising of waxes within an ink to the surface, as a means of imparting scuff resistance to the dried ink film.