What liquids glow under a black light?

Answer 1

White paper is treated with fluorescent compounds to make it appear brighter. Historical documents that have been forged can sometimes be detected by placing them under a black light to see if they fluoresce; fluoresces have only been used in paper made after about 1950.

Club soda or tonic water contains quinine, a bitter-tasting fluorescent compound that glows blue-white under a black light.

Vitamins (specifically vitamin A, thiamine, niacin, and riboflavin) fluoresce strongly. A small piece of a vitamin B-12 tablet crushed and dissolved in vinegar glows a bright yellow under UV light.

Chlorophyll fluoresces with a blood red color. Grind spinach or swiss chard with ethanol and filter the resulting chlorophyll extract. Bright white light can be used to drive the fluorescence. Place the extract in a petri dish on top of an overhead projector lamp in a darkened room to get the full effect.

Antifreeze fluid contains additives that fluoresce. Investigators sometimes use black lights to look for antifreeze splashes on pavement and vehicles to reconstruct automobile accident scenes.

Laundry detergents contain fluoresces to make the whites "whiter than white". Detergent residues on white clothing causes it to glow blue-white under a black light. These fluoresces sometimes make white clothing appear blue in color photographs.

Dental enamel and whiteners also contain fluorescent compounds that fill in the blue part of the spectrum to prevent the enamel from appearing too yellow.

Postage stamps are printed with inks that contain fluorescent dyes.

Answer 2

Some liquids that glow under a black light include tonic water (due to quinine), some laundry detergents (containing optical brighteners), highlighter ink, and certain hand sanitizers. These substances contain molecules that absorb the ultraviolet (UV) light from the black light and re-emit it at a longer wavelength, creating a visible glow.