Effect of Ink Water Pick-up on Printability in a High Speed Lithographic Press

Tests were conducted on a high speed we lithographic press to determine the effect of ink water pick-up on print quality. Density, dot gain, gloss, trap and mottle were all measured. On an overall basis, the ink set having low water pick-up (LWPU) demonstrated excellent print quality and was easy to run. A high water pick-up (HWPU) set of inks had good print quality and was also easy to run. When the HWPU ink set was adjusted to LWPU with an additive, (AWPU) print quality deteriorated and runnability suffered. Visual rating of prints using seven experienced panelists agreed with objective measurements of print quality. The LWPU ink set was rated best, the HWPU set was rated second best, and the AWPU ink was third. Results with the AWPU set confirm that the use of additives to decrease WPU to a given specification value has a detrimental effect on print quality. Visual rating of prints using seven experienced panelists agreed with objective measurements of print quality. The LWPU ink set was rated best, the HWPU set was rated second best, and the AWPU ink was third. Results with the AWPU set confirm that the use of additives to decrease WPU to a given specification value has a detrimental effect on print quality. Print quality for all ink deteriorated significantly when speed was decreased to 1,000 fpm. Water pick-up was significantly lower with fountain solution than distilled water in the Duke test (ASTM D4942). An in-depth study is planned using a wide variety of fountain solutions to learn more about this phenomenon.