Heatset Ink

A quick-drying type of ink that dries by evaporation of its solvent in a high-temperature drying oven followed by cooling to set the ink. Heatset inks comprise the pigment, a solvent (a heatset oil), a litho varnish, and a wax compound modifier. In heatset drying, the printed web is passed through a high-temperature dryer (typically at 250:500ºF) which evaporates the solvent. A chilling procedure (utilizing chill rolls) then cools the ink down to about 75:90ºF. Chemical reactions and absorption also set the ink. (See also Heatset Drying.)

Heatset inks are used in letterpress and offset lithography, typically in web presses, and have the advantage of quick drying, which reduces the risk of excessive ink spread and absorption. The process, however, can cause problems in coated paper which, if of insufficient porosity, can blister during heatset drying. (See Blistering and Fiber Puffing.)

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