A lot of everyday materials glow under a black light. The ultraviolet light emitted by black light is absorbed by fluorescent substances and re-emitted, making a longer wavelength of light visible and making the fluorescent substances look as if they glow.
Paper, Jelly and Beverages
White paper shines under black light because of the florescent chemicals added to whiten the paper. Petroleum jelly, such as Vaseline, glows as well. Quinine, which is in tonic water and club soda, makes those beverages shine a white-blue in black light.
Vitamins, Fluids and Chlorophyll
Vitamins A and B, niacin, riboflavin and thiamine all shine under black lights. Blood, semen and urine contain florescent molecules, which make them visible under black light. Grinding up plants into a chlorophyll-type paste makes them illuminate a red shade under black light.
Teeth Whiteners and Stamps
A lot of teeth whiteners contain special blue compounds to make teeth appear white instead of yellow. These compounds glow blue under black light. Postage stamp ink contains florescent elements that glow under black light as well.