What Substances Show Up Under a Black Light?

Written by beth richards | 13/05/2017
What Substances Show Up Under a Black Light?
Only certain things glow, or fluoresce, under a UV light. (neon glow image by Laura Lupton from Fotolia.com)

Popular crime shows depict officers and crime scene investigators using UV, or black lights, to show incriminating fluids but you might be surprised to learn what other things show up under a black light. Certain items glow, or fluoresce, under a black light because their molecules absorb the shorter wavelength of the UV light and give off a longer wavelength.


Certain fluids fluoresce. Club soda contains quinine, which glows when you place it under a UV light. Antifreeze fluid, some inks and dyes, urine, semen and blood all fluoresce under black light.

Vitamins and Minerals

Minerals like opal, quartz, amber agate and gypsum glow under a black light. Vitamin A and niacin, riboflavin and thiamine react to black light. According to chemistry.com, a crushed B-12 vitamin mixed with vinegar glows bright yellow under a UV light.

Bacteria and Fungus

Fungus, mould and bacteria show up under a UV light. The U.S. Library of Medicine notes that dermatologists use a black light to perform a test called a Wood's Lamp Examination to look for bacterial and fungal infections, skin infections and signs of certain other illnesses that are apparent on the skin.

Other Substances

Petroleum jelly fluoresces under UV light because it contains uranium, according to the Environmental Protection Agency (EPA). Canary glass, a type of antique yellow glassware, also contains trace amounts of uranium and will glow under a black light. Common, everyday items such as laundry soap and white paper also fluoresce. Jellyfish and scorpions glow in black light.

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