Print Drying

Litho inks dry by absorption and auto oxidation. They consist of resin, pigment, dryers and a distillate. The distillate reduces the viscosity of the ink so it soaks into the paper more readily; it then sets but the drying reactions may take 2 days to complete. To prevent sheets from sticking together and spoiling, anti set-off powder is used to separate them and allow air to assist oxidation.
IR reduces the viscosity of the ink while in its liquid phase so it penetrates the paper more rapidly though absorption rates depend on the type of paper. It also accelerates drying by increasing the stack temperature and so increasing the rate of oxidation. The greatest benefits are obtained with a stack temperature of between 35-40 C.
IR can be used with all conventional printing inks except UV curing ones. Water cooled reflectors are available to keep the heat to the machine and its surrounding areas to a minimum. Papers with densities as low as 50-60 g/m2 can be dried.