Printed Density as Related to Water Absorption by Lithographic Inks.

Previous researchers have reported that inks containing as much as 40 percent water print without any substantial reduction in density due to the presence of the water in the ink. Our findings cause us to reach very different conclusions which show considerable change in density with increasing water content in inks. Experimental data were obtained by measurements of optical densities of ink layers of specifically varying thicknesses containing predetermined quantities of water. The data were found to be in excellent agreement with predicted results obtained by calculations based on Tollenaar's equation D=D (1-e-mx) which relates optical density D to ink layer thickness x. (D is the saturation density, m is the increase of D/D per unit increase of ink layer thickness at low values of x.) The data allow derivation of mathematical relationships concerning density, percentage of absorbed water in ink, and ink layer thickness. One can given range of optical densities as well as predict the amount of water absorbed in an ink which produces a particular printed density.