Viscosity can be simply defined as the internal resistance to flow. The more viscous a printing ink is, the
slower or more difficult, comparatively, its passage through pumps, pipes and filters, the slower will be its
absorption by paper, the sharper it will print, the less it will strike through and the less it will tend to
misting. These statements on relations between viscosity and printability naturally apply only within the
limits of commonly used newsinks. The greater the mean molecular weight of the total binding agent and
the higher the pigmentation, the greater will be the viscosity
Viscosity is a measure of a liquid’s ability to resist flow. A thick liquid that does not flow easily has high-viscosity; a thin liquid that readily flows has low-viscosity. The viscosity of ink strongly affects how it behaves on the press and is ultimately transferred to the sheet.
Consider two parallel plates of area A.
The distance between these plates is x.
The space between the plates is filled with a liquid, which can be regarded as a series of very thin plates sliding one over another.
To move one plate with velocity v, some Force F has to be applied.