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Black lights emit a very dim, purplish light that sets a great mood for a party. Halloween parties or haunted houses often use black lights, but these lights can also help to create a fun, neon, glowing atmosphere for any occasion.
Why Things Glow
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A black light emits ultraviolet rays that are very bright, but humans can't see them. Fluorescent objects absorb the ultraviolet light rays given off by a black light so that human eyes can see it.
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Fluorescent Neon Objects
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Neon-colored fluorescent paper, clothing or highlighter ink glows under the black light. Special black-light fluorescent paint and markers are sold at most craft stores. The color will appear about the same as in normal light but much brighter.
Other Fluorescent Objects
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Some other common objects glow under a black light. White t-shirts typically glow bright under a black light. Typically, this is due to the bluing agents in laundry detergents that are phosphors reacting to the ultraviolet light rays from the black light. The new $20, $50 and $100 U.S. bills (those made after 2003) also have a security thread through it that reacts to black lights.
Phosphorescent Objects
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A phosphorescent glow can last a few minutes even after the black light is turned off. Many glow-in-the-dark products will also work in black light. Petroleum jelly looks nearly invisible in normal light but glows brightly in black light.
Blocking Black Light
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To put black light on some parts of a room and not others, try a shield that blocks the UV rays. Quartz glass and automotive glass work well. Special lighting-filter gel will stop the ultraviolet rays but allow normal light through.