Paper Base

A nother factor that affects the amount of colors reproducible by the subtractive process s the type of substrate – usually paper – used to print the image.

As discussed earlier, offset printing uses transparent color inks that act as filters an subtract portions of the white light striking the image on paper to produce other colors. It is the paper that reflects any unabsorbed light back to the viewer. Paper stocks vary in color, gloss, brightness, texture and absorbency.

A press that prints on coated paper produces a wider range of colors than a press that prints on uncoated paper. This is because the rougher surface of the uncoated paper scatters the light and reduces the amount of light reflected back to the viewer. Smooth, glossy white paper returns more light back to the viewer. The range of colors on a substrate such as newsprint, which is usually rough, uncoated and yellowish, is more limited. A paper with a bluish cast will absorb some red and green wavelengths and cause colors to appear grayer than if printed on white paper. The effect of the paper base is so important to the appearance of a printed sheet that it can be considered a fifth color.