Coated Versus Uncoated- Why the Difference In Density?

It is well known in the industry that you can get richer colors (higher density) on coated stock than on uncoated stock. One common explanation is that ink does not transfer well to a rough, uncoated stock. A second explanation is that ink soaks into an uncoated stock. The paper fibers, in effect, hide the ink so that some of the pigment is lost. Another common explanation is that there is an incomplete lay-down of ink on uncoated stock. According to this explanation, the uneven topography of the paper fibers results in pinholes where white paper shines through.

A few simple experiments will be presented which show that the main reason that ink on a coated stock is richer than the same ink on uncoated stock has to do with how the surface reflected light is scattered from the two surfaces.