1. An opaque paint used in the production of neon signs to block out the crossover connections between letters. Special paints have been formulated for this purpose that offer a high degree of adherence to glass,as well as resistance to weather,heat,light,high voltages, and corona discharge. Paints with metallic bases should be avoided because of their ability to conduct electricity. 2. A type of liquid mask used to seal accidental holes in a stencil in areas not intended to be screen-printed.