An investigation of the applicability of Walker and Fetsko ink transfer equation on and the influence of ink viscosity on heat set ink used on the web offset process
The Walker and Fetsko ink transfer equation is the most used ink transfer equation to predict the ink and paper behavior on the ink transfer step in the printing process. All previous studies have shown that this equation is mostly applicable in the three major printing processes, letterpress, lithography and gravure. A study by Schaeffer, Fisch and Zettlemoyer reported extensive measurements for several oil-base ink and paper combination over a range of proof-press printing conditions. Yuri Bery did a series of studies for modifying the Walker and Fetsko equation in gravure inks for Weyerhaeuser Company. All the studies showed that although generally the Walker and Fetsko ink transfer equation can be applied to all three major printing processes, there are always some modifications needed for different rheological characteristics and printing conditions . The trends for the lithographic process is toward Web Offset printing. The components of Web Offset ink is quite different from conventional sheetfed lithographic ink in the pigment and vehicle used. This paper is to find out if the Walker and Fetsko ink transfer equation can be also applied to the Web Offset ink. By investigating the effect of viscosity - one of the most important characteristics in rheology of ink - on the transfer parameters, the ink transfer mechanism model can be examined to see whether it is the same for oil base ink as for the heat-set Web Offset ink. The result of this experiment showed there is a significant different absorption behavior between coated paper and uncoated paper. This difference is effecting the applicability of the Walker and Fetsko ink transfer equation in this particular type of ink and paper combination
