There are also inks and dyes that contain fluorescent ink that can "invisibly" mark items, which can be used for anything from passing secret notes to marking items to be recognizable if stolen.
White and neon colors react the best, especially orange, yellow, pink, and green.īlack light bulbs are used to authenticate oil paintings, some antiques, and catch counterfeit currency. You've probably been to a bowling alley or college party that used black lights to make clothing glow. Ultra-violet light causes some materials to glow or fluoresce, which is brought out by blocking most of the light in the visible spectrum. BL black light bulbs tend to skew more towards a blue light than purple and are made for use in bug zapper insect traps. These black lights are labeled "blacklight" or "BL" since they lack the blue filter that gives the first type the name. The second kind can look like a standard fluorescent tube. The filter causes these bulbs to look purple or dark blue even when turned off. Black lights with the blue filter coating are called "blacklight blue" or "BLB" by manufacturers. When you think of black lights, you're probably thinking of the first kind. A bulb can either use a filter to block most visible light and only allow ultraviolet light through or it can produce ultraviolet light and limited light in the visible spectrum. A black light is a bulb that emits ultra-violet (UV-A) light and not much visible light.
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