Blacklites are a subset of fluorescent lamps that are used to provide short-wave ultraviolet light (at about 360nm wavelength). They are built in the same fashion as conventional fluorescent lamps but the glass tube is coated with a phosphor that converts the short-wave UV within the tube to long-wave UV rather than to visible light. The UV radiation of Blacklite excites the fluorescent paints, fabrics, and other materials used for theatrical special effects. Some common uses of Blacklite lamps are for lighting effects in bars and restaurants, detecting materials invisible in visible light and in bug zappers to attract insects.
Blacklite Blue lamps are also made from more expensive deep purple glass known as Wood’s glass rather than clear glass. The deep purple glass filters out most of the visible colors of light directly emitted by the mercury-vapor discharge, producing proportionally less visible light compared with UV light. This allows UV-induced fluorescence to be seen more easily. Commonly used in psychedelic shops for more dramatic effects with blacklite posters and displays. In the theatre Blacklite Blue is used where only fluorescent materials in clothing and objects, most white clothing, teeth, and whites of the eye, are desired for effect. Often used in bars and restaurants to achieve similar effects.