Black lights emit light in the ultraviolet (UV) range of the light spectrum. The paint glows because it is florescent and absorbs the UV light. The paint then produces visible light that appears to glow. Black light interacts with white and bright neon colored paint. Paint that emits visible light is luminescent paint. Florescent and phosphorescent paint safely emit visible, glowing light, while radioluminescent paint uses an unsafe radioactive isotope to provide light.
Florescent paint contains pigment that absorbs the black light and emits visible, glowing light. The UV radiation interacts with the florescent material in the paint. Many white and lighter paints already contain florescent characteristics and glow under UV light. If you are unsure about a paint's florescent characteristics, ask a paint store clerk which paints glow in black light. Test the paint by putting a black light over it. If it does not glow or you want the the paint to glow brighter, add a brightening agent, such as Rit Color Brightener. Simply dissolve the powder in water and add to the paint. If the paint is oil-based, mix the powder into the paint.
Phosphorescent paint is also known as "glow-in-the-dark" paint that glows a greenish-blue color. Similar to florescent paint, the minerals in phosphor react with the UV light, absorb it and emit a soft, visible light. The light persists for a short period of time, about an hour, after it has absorbed the light. Phosphor, as used in paint and glow-in-the-dark plastics, is easily made non-toxic for production.
Radioluminescent paint glows without exposure to a black light. It is self-lunimous. The paint contains a radioactive isotope called radionuclide. As the isotope decays and breaks down, it emits electrons (negative energy) that move very quickly, producing visible light. Like other radioactive materials, radionuclide requires knowledge of the substance and potential adverse health affects associated with radiation.
Florescent paint is commonly used in bowling alleys for "cosmic bowling," arcades and black light parties. Colored pigment is added to white florescent paint to create a variety of colors. Phosphorescent paint and plastics can be found in star and moon glow-in-the-dark decals, glow sticks used at raves, night clubs and t-shirts. Radioluminescent paint is not commonly used today, with an exception being diving watches. In the 1920s and '30s, it was used for airplane controls and watch faces.