The Printing Problems Created by the Use of Reduced VOC Wash-up Solvents and Their Effect on Press Productivity

This paper recounts the problems printers in Southern California have experienced in their mandated use, over a period of one year, of reduced VOC (volatile organic compound) wash-up solvents containing not more than 500 grams per liter of VOCs, and their ongoing tests of very low VOC solvents, i.e., solvents containing not more than 100 grams per liter of VOCs. It also recounts laboratory tests that demonstrate the adverse effect that reduced VOC solvents can have on the lithographic process and which are also being used to screen very low VOC solvents as a prerequisite to on-press testing. Additional information on the behavior of reduced VOC solvents was and is being obtained from three sources: (1) the responses of 74 printers to a survey of their initial experience in using 500 grams/liter solvents, (2) visits to printing plants, and (3) both short term and controlled long term printing tests. The evidence obtained to date from these sources indicates that the most important of the problems experienced by printers are caused by two phenomena: absorption of solvent by the rubber rollers during washups of the inking system rollers, and solvent drips resulting from fugitive solvent hideout during blanket and back cylinder cleaning. Because all of the remedies to the problems that have been developed to date reduce press productivity, a spreadsheet was designed for assessing the effect that a given low VOC solvent has on press productivity. The paper also presents an example of results obtained using this spreadsheet.