By non-porous" in the description of the present invention it is meant that ink, paints and other liquid coloring media will not readily flow through the substrate (for example, less than 0.05 cm3.sec-1 at 9.3???102 Pascals (7 mm Hg) pressure, preferably less than 0.02 cm3.sec-1 at 9.3???102 Pa pressure).