The Ignite® line of liquid fluorescent colorants is compatible with Smooth-On urethane rubbers, urethane plastics, urethane foams (rigid and flexible) and silicones. The fluorescent or "glow" effect is maximized under ultra-violet light or "black light." The most dramatic color effect is realized when an Ignite colorant is used with a clear or translucent urethane rubber (such as Clear Flex 50) or plastic (such as Smooth-Cast 325).The NEW Ignite® 9 pack gives you the opportunity to experience each color without spending a lot of money.What Makes Castings Made With Ignite® Pigments Appear To Glow? When you add Ignite fluorescent color to a urethane material, more ultraviolet light from the cured material is visible to your eye vs. castings made with SO Strong® colorants. The casting appears brighter in ambient light and appears to glow under ultraviolet light.