Impact of fountain solution addition level on tack and optical properties of the print of a mechanically distributed water-in-oil thin film emulsion

The impact of addition and evaporation of an alcohol/surfactant stabilised fountain solution and offset ink thin film emulsion has been studied using a printing ink application device. The ink rheology testing technique (TackOscope), incorporating the possibility to apply the aqueous liquid (print fountain solution) to mix into an oil-based ink to create an emulsion in a twin roll nip, was used firstly in its standard form to provide information relating to the tackiness property during emulsification. The ink used showed a continuous tack increase over time, superposed on this trend, and addition of intermediate amounts of fountain solution were shown to decrease the tack of the emulsion monotonically. After evaporation, the tack finally returns back to its expected undisturbed level, following a fountain solution-free ink tack development, the result being a sigmoidal evolution of tack recovery to this point. Secondly, by introducing a defined non-absorbent substrate in a single pass between the rollers, transfer of the emulsion could be achieved. Expressing the behaviour as a function of the emulsion component to ink ratio, it was, therefore, possible to study the influence on the optical properties of the final thin layer in the form of a print.