How to Use Black Light

By Elliot Volkman ; Updated November 30, 2018
Black light lit room

A common decorative element found in college apartments and dorms is the black light. Black lights can also be used as party elements or to change a boring room into an inverted rave. Using the appropriate, complementary paints and clothing will enhance the effects of black lights. Black lights can also be used to identify counterfeit money, human or animal waste and hand-stamp identification, and it can even allow you to write hidden messages.

Place the black light fixture on a wall facing the center of the room or on the ceiling when you are setting up for a party. Using more than one black light fixture is recommended to light the room better.

Wear a white or a bright neon T-shirt to spread the effects of the black light. Placing black light paint on walls, posters and even people will create an interesting atmosphere for parties.

Identify whether a dollar bill is counterfeit or legal tender by placing it under a black light bulb. The black light bulb will detect the special security strips in any bill except the $1 bill. A watermark will also be revealed under a black light.

Locate human or animal waste by sweeping a black light over furniture, sheets and carpets in a darkened room. A black light will make it easier to identify places where waste could be located in a dark area. Often excreted liquids will be more apparent under black lights.

Place a black light at the entrance of a bar or club that uses invisible ink to indicate whether a cover fee has been paid or patrons are of age. Lemon juice can also replicate the effect of the invisible ink pen, which can cause an issue for those who are looking for these marks on their patrons.


Change the symbol or marking daily to make it more difficult to mimic if you are using invisible ink to identify patrons.


Black lights alone do not provide much actual light in a room unless color enhancements are placed throughout the room.