The best kind of party light
Fluorescent black light tubes are typically made in the same fashion as normal fluorescent bulb except that a phosphor that emits UVA light instead of visible white light is used. The type most commonly used for black lights, designated "blacklight blue" or "BLB" by the industry, has a dark blue filter coating on the tube, which filters out most visible light, so that florescence effects can be observed. These tubes have a dim violet glow when operating. They should not be confused with "blacklight" or "BL" tubes, which have no filter coating, and have a brighter blue color. These are made for use in ''bug zapper" insect traps, where visible light emission is not a problem.