A process used to produce a printing ink pigment that involves dispersing the pigment particles in oil, rather than water. Typically, pigments begin life as a water suspension of pigment particles, which are then filtered out of the suspension and dried into a press cake. In flushing, the particles are not dried after filtering, but are left with a water content of 30:80%; the resulting press cake is mixed with oil, which then disperses the water. The remaining bits of moisture are removed via suction and/or heat. Flushing is performed on pigment particles that, in the traditional method of drying, form hard-to-grind clumps. The paste generated by flushing produces finer-dispersed particles. In some cases, the manufacture of pigment is faster, easier, and less expensive when pigment is produced using the flushing process. Pigments can be flushed in a variety of different liquids, depending on the end-use characteristics of the ink. Newsink is flushed using mineral oils, and other types of inks use anything from litho oils to gloss ink varnishes. Pigments produced by flushing are called flushed colors.
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