The clear coat 902 is selected to wet the surface of the holes 704 appropriately for the material in which the holes 704 are formed. In one embodiment, a UV curable clear coat 902 having a viscosity (when liquid) matched to the dimensions and materials of the holes 704 was painted or sprayed upon the opaque outer surface 702, allowing the natural surface tension properties and capillary action of the clear coat liquid to draw the clear coat 902 into the holes 704. Thereafter, the clear coat 902 was appropriately cured. Depending upon the circumstances of the particular application in which the present invention is being utilized, the clear coat 902 may be applied from the opaque outer surface 702, the rear surface 804, or both surfaces.

It has been discovered that the clear coat 902 provides several aspects. For example, it closes and seals off the holes 704, protecting them from ingress of dirt, oil, and other contaminants that might degrade the light transmissivity thereof. The outer surface is thus secured in case of exposure to contamination.