Fundamental Studies of Linting: Understanding Ink-Press-Paper Interactions Non-Linearity

The linting propensity of paper is the tendency of paper to shed loosely bonded surface fibres in offset printing. A model based on three forces that describe the complex interactions between ink, the paper surface, and the press conditions that create linting is briefly presented. Two forces are related to free and porous ink flow in the printing nip, and the third one is based on ink filament elongation after the printing nip. The model fully explains the synergy between printing pressure, press speed, ink viscosity, paper roughness, and pulp furnish mix. Results from printing on Dynamic Sheet Former samples are detailed. Due to the non-linearity and the synergy between linting and the various parameters, it is shown how, with the right combination, a low printing pressure can produce more lint than a high printing pressure, that a low viscosity ink can produce more lint that a higher viscosity, higher tack ink, and that, at low ink level, low printing speed can produce more lint than a higher printing speed. It is also shown that the speed effect is related to a threshold resistance of the paper surface to fibre removal. By comparison, the paper roughness and the pulp furnish have less effect on linting than the press parameters.