Ed #9 Understanding Ink

On press, ink is dispensed from ink fountains (one for each color) onto a series of rollers. The ink rollers then spread the inks onto the imaged areas of the plate. Meanwhile, other rollers apply water, which repels the oily ink, to the non-imaged areas of the plate in order to keep the ink from covering them. Each plate then transfers the ink to a rubber blanket that in turn transfers the ink to the paper.

To work well, ink must balance a number of often conflicting characteristics. It must be liquid in order to spread evenly across the plates, but it also must dry quickly, to avoid smudging. It must be sticky—or tacky—enough to stay exactly where it is put, but not so sticky that it pulls the coating away from the surface of the paper.

Ink experts use a number of terms to describe the different characteristics of ink, including viscosity, body, opacity, and light fastness or color permanency. An ink’s viscosity, which changes under the heat and pressure of the printing process, is the degree to which the ink resists flowing. “Body” refers to the ink’s overall consistency, which can range from soft and pliable to stiff and rigid. The opacity of the ink is the degree to which it allows the whiteness or color of the stock to be visible to the viewer. Light fastness or color permanency is determined by the chemistry of the ink’s pigments and their ability to resist a shift in color caused by UV radiation or heat.