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Abstract
In offset printing, print quality depends on balance of the feeding amount of ink and fountain solution. It is well known that ink/fountain solution on printing press co-exist in the form of W/O emulsion. In this report, the surface of ink films and water-droplets formation on them have been investigated by the observation through emulsion visualization apparatus developed in our research center. It was made clear that the surface of any ink film on a roller is not flat during rollings and that surface water-droplets appear on the emulsified ink film at a certain water content, which greatly effects the properties of emulsified ink. The IPA-substituted reagent has been selected by examining the emulsifying characteristics on the ink tester and printing machine among several kinds of surfactant solutions in order to come to close to the aqueous IPA solution as a standard solution, which exhibits the metastable emulsified state. Further, the role of fountain solution in image production on plates by emulsified ink film has been discussed. The IPA-substituted reagent has been selected by examining the emulsifying characteristics on the ink tester and printing machine among several kinds of surfactant solutions in order to come to close to the aqueous IPA solution as a standard solution, which exhibits the metastable emulsified state. Further, the role of fountain solution in image production on plates by emulsified ink film has been discussed.