LUMINOUS PAINT

paint that glows in the dark because it contains a phosphor, a substance that emits light for a certain length of time after exposure to an energy source, such as ultraviolet radiation. Zinc sulfide and calcium sulfide are such phosphors. Some luminous paints contain a source of radiant energy, such as salts of radium. These paints glow indefinitely and are used for painting dials and signs to be read at night.