Lithographic fountain solution

Duplicator and Business Form Inks. Duplicator sheet-fed machines require very press-stable yet quicksetting inks. They must also possess good lithographic properties of wide tolerance for fountain solution and provide good printing properties on a wide variety of uncoated papers. 

An overview of the lithographic process is presented with particular emphasis on the role that surface and colloid chemistry plays. Recent research has shown the importance of these chemistries in fountain solution, ink and plate interactions and the effect of these interactions on the dynamic behavior of the lithographic ink on press. Data on the rheological behavior of preformed fountain solution/ink emulsions is presented along with an evaluation of prints made with the inks on an actual press run. The importance of pre-testing the emulsification behavior of printing inks in predicting their printability is demonstrated. 

In order for a lithographic ink to move smoothly and uniformly through the press to the substrate, it is essential that the ink be able to absorb a reasonable quantity of the fountain solution being used as emulsified droplets. Many authors have observed this fact (Banks, (1), Surland (15,, MacPhee (18)) and... 

However, the ink as actually printed on a lithographic press is an emulsion which may contain as little as 20% or as much as 50% of fountain solution as a finely dispersed internal phase. It is the rheology of this ink emulsion which determines the configuration of the printed areas and the faithfulness of the reproduction of the plate image. 

In this investigation, a set of six experimental heatset lithographic inks were subjected to a variety of rheological measurements both as a dry ink, as well as after being emulsified with a commercial fountain solution. Determinations of apparent viscosity at 2500 secs l and yield stress at 2.5 secs l were made 25°C from 5 point shear rate/stress curves, and inkometer tacks at 1200 RPM/90°F were also measured. 

Can these results for water sorption be related to the application of fountain solution to paper during lithographic printing In Figure 16 the addition of a surfactant is seen to have little effect on the dynamic surface tension of water at a surface age of 3 ms. Thus, on the time scale of the wetting of newsprint, fountain solutions which consist principally of an aqueous solution of gum arable may behave similarly to the case of water alone. Conversely, as shown in Figure 17 fountain solutions containing isopropanol exhibit lower dynamic surface tensions and should wet paper more readily than water alone. 

Lithographic inks Inks used in the lithographic process. The principal characteristic of a good lithographic ink is its abihty to resist excessive emulsification by the fountain solution. 

Ductor Roller n The roller which is in intermittent contact with the fountain roller and transfers ink to the distribution system of the press. On a lithographic press it is also the roller which transfers the fountain solution to the dampening rollers. 

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