Effects of ink: Fountain solution interactions on piling in heatset printing

In this study on-line measurement devices were utilized to clarify how the changes in fountain solution properties affect formation of non-image area piling during printing. On-line measurements of pH, conductivity, redox potential, temperature, and calcium content were installed to measure fountain solution quality. Chemical impurities in the fountain solution cycle are mainly due to dissolution of ink. The dissolution increases concentration of dissolved cations such as aluminum and calcium, which increases hardness and conductivity. This has implications both to the press runnability and product quality. Non-image area piling on blanket originates from the plate. Ink spreads to the non-image area of the plate and ends up on the non-image area of the blanket. A part of it continues further to the paper. On-line measurements of water, ink pigment, and ink binder were used to follow the interactions of ink and fountain solution on plate and blanket. The findings were verified by visually observing the press with triggered micro-imaging. When fountain solution feed level is correctly adjusted, the main reason for the non-image area piling is poor ink stability on the plate. High amounts of cations in fountain solution may separate ink pigment particles from the ink binder. The phenomenon is seen as ink pigment particles on the non-image area of the plate, and it is significant especially when the same fountain solution has been utilized for a long period of time.