Transport of Immiscible Vapor Pressure Contrasting Liquids in Multiple Nip Impressions: Application to Heatset Offset Printing of Paper

Abstract

A multistation heatset offset printing press was studied here to exemplify the transport of immiscible liquids into a porous substrate under dynamic rolling nip conditions. In offset printing, oil-based ink and a water-based fountain solution are used to define the image and nonimage areas according to the respective surface energy of the printing plate. The fountain solution and ink inevitably form an emulsion after the press has run sufficiently to reach equilibrium. It is this emulsion that is transported via a rubber blanket to the paper and forms the printed image. The emulsification degree depends on the ink properties and the printing process at the equilibrium ink–fountain solution balance, which, in turn, supports stable continuous running of the press in order to achieve a good print quality. Focus is given to the transfer of fountain solution to both nonimage areas of paper as well as to the inked areas carried in the emulsion. In order to monitor the amount transferred, each of two tracing ele...