A Model for Ink/Water Balance in the Lithographic Process

A simple model quantitatively describing the ink/water balance in offset printing has been developed. A new parameter, the water redistribution ratio, is introduced. An analysis of experimental data from the literature indicates that the water redistribution ratio decreases as the water pickup coefficient increases, providing the first indirect evidence that splitting of a composite film, consisting of a water layer and an ink layer, indeed occurs within the low tack, low viscosity water layer, as speculated by many researchers. The model also predicts that the water consumption rate may increase, be independent, or decrease with increased image coverage, depending on the amount of water evaporated.