OFFSET INK TACK AND RHEOLOGY CORRELATION: - I: ink rheology as a function of concentration

This paper is divided into two parts with the aim to compare visco-elastic structure relaxation of a presheared offset ink with observed ink tack development on a representative absorbent multi-coated paper. The methods used include oscillatory and shear rheometry in part I, and comparison with the SeGan Ink Surface Interaction Tester (ISIT) in part II. By diluting the ink with mineral oil, a plot of viscosity against solids content could be established. The viscosity of the progressively diluted ink was then extrapolated back toward increasing concentration. In this way a relation is developed between the viscous character of the ink at a given concentration and that of the ink as it will be on the substrate, i.e. effectively the ink-on-paper viscosity and solids content in respect to the tack force measurement. This novel approach allows the solids and viscous parameters of the ink to be analyzed as the initial ink setting actually occurs on real papers, as discussed in part II.