The effect of tap water and fountain solution on sheet-fed offset print quality

The goal of this project was to clarify the effect of tap water and fountain solution on print quality in sheetfed offset printing because the seasonal variations in raw water are significant in Finland. The project was performed during 2001-2003 at VTT. Other participants of the project were Graphic Industry Research Foundation, M-real (paper maker), Hostmann-Steinberg (ink maker) and two printing plants: Otavan Kirjapaino Oy and Lönnberg Painot Oy. The research work contained the following parts: Material analysis from tap water, fountain solution, ink, paper and print: Comparison of three emulsification devices (Hydroscope, Duke and Lithotronic): Correlation analysis with a multivariable program SIMCA: The printing tests were performed in the printing plants during 2-3 weeks test cycles in spring, autumn and winter. The samples were taken at the beginning and at the end of each cycle. Main results of the project were: The quality of tap water does not depend on seasonal variation of raw water. Clean and dirty fountain solutions have quite similar emulsification behavior. The three emulsification devices give quite similar results with maximum emulsification capacity. Double coated woodfree paper (DCWF) can induce a calcium impact in fountain solution which have an effect on printability. A new method to determine rubbing resistance of the print was developed. Seasonal variations have an effect on the dot parameters and rubbing resistance of the print. At printing plant A: Conductivity, pH and solid content of tap water correlated with pH and conductivity of fountain solution. At printing plant B: Ash and solid content of tap water correlated with pH of fountain solution. Seasonal variations, Fe-content of fountain solution and ink type have a combined effect on dot parameters and rubbing resistance of the print.