THINGS THAT GLOW UNDER BLACK LIGHT - Fluorescent substances absorb the ultraviolet light and then re-emit it almost instantaneously. Some energy gets lost in the process, so the emitted light has a longer wavelength than the absorbed radiation, which makes this light visible and causes the material to appear to glow. Fluorescent molecules tend to have rigid structures and delocalized electrons.

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Fluorescent Substances And Black Light

16 Things That Glow Under Black Light

by Anne Marie Helmenstine, Ph.D. 

There are a lot of everyday materials that fluoresce or glow when placed under a black light.

A black light gives off highly energetic ultraviolet light. You can't see this part of the spectrum, which is how 'black lights' got their name.

Fluorescent substances absorb the ultraviolet light and then re-emit it almost instantaneously.

Some energy gets lost in the process, so the emitted light has a longer wavelength than the absorbed radiation, which makes this light visible and causes the material to appear to glow.

Fluorescent molecules tend to have rigid structures and delocalized electrons.

Tonic Water Glows Under Black Light

The bitter flavoring of tonic water is due to the presence of quinine, which glows blue-white when placed under a black light. You'll see the glow in both regular and diet tonic water.

Some bottles will grow more brightly than others, so if you're after the glow, take a pen-sized black light with you to the store.

Glowing Vitamins

Vitamin A and the B vitamins thiamine, niacin, and riboflavin are strongly fluorescent. Try crushing a vitamin B-12 tablet and dissolving it in vinegar. The solution will glow bright yellow under a black light.

Chlorophyll Glows Red Under Black Light

Chlorophyll makes plants green, but it fluoresces a blood red color.

Grind some spinach or swiss chard in a small amount of alcohol (e.g., vodka or Everclear) and pour it through a coffee filter to get chlorophyll extract (you keep the part that stays on the filter, not the liquid).

You can see the red glow using a black light or even a strong fluorescent bulb, such as an overhead projector lamp, which (you guessed it) gives off ultraviolet light.

Scorpions Glow in Black Light

Some species of scorpion glow when exposed to ultraviolet light. The emperor scorpion normally is dark brown or black, but it glows a bright blue-green when exposed to black light. The bark scorpion and European yellow-tailed scorpion also glow.

If you have a pet scorpion, you can check to see whether or not it glows using a black light, but don't keep it exposed to ultraviolet light for too long or it can suffer damage from the ultraviolet radiation.

People Have Stripes Under Ultraviolet Light

Humans have stripes, called Blaschko's Lines, that may be observed under a black or ultraviolet light. They don't glow so much as become visible. 

Tooth Whiteners Glow Under Black Light

Tooth whiteners, toothpaste, and some enamels contain compounds that glow blue to keep teeth from appearing yellow. Check your smile under black light and see the effect for yourself.

Antifreeze Glows in Black Light

Manufacturers purposely include fluorescent additives in antifreeze fluid so that black lights can be used to find antifreeze splashes to help investigators reconstruct automobile accident scenes. Antifreeze is so fluorescent, it glows even in sunlight!

Fluorescent Minerals and Gems Glow in Black Light

Fluorescent rocks include fluorite, calcite, gypsum, ruby, talc, opal, agate, quartz, and amber. Minerals and gemstones are most commonly made fluorescent or phosphorescent due to the presence of impurities.

The Hope Diamond, which is blue, phosphoresces red for several seconds after exposure to shortwave ultraviolet light.

Body Fluids Fluoresce Under Black Light

Many body fluids contain fluorescent molecules. Forensic scientists use ultraviolet lights at crime scenes to find blood, urine, or semen.

Blood does not glow under a black light, but it reacts with a chemical that does fluoresce, so it can be detected after this reaction using ultraviolet light at a crime scene

Banknotes Glow Under Black Light

Bank notes, especially high-value bills, often glow under ultraviolet light. For example, modern US $20 bills contain a security strip near one edge that glows bright green under a black light.

Laundry Detergent and Other Cleaners Glow Under UV Light

Some of the whiteners in laundry detergent work by making your clothing a bit fluorescent. Even though clothing is rinsed after washing, residues on white clothing cause it to glow bluish-white under a black light.

Blueing agents and softening agents often contain fluorescent dyes, too. The presence of these molecules sometimes causes white clothing to appear blue in photographs.

Banana Spots Glow Under Black Light

Banana spots glow under UV light. Who knew? Shine a black light on a ripe banana with spots. Check out the area around the spots. 

Plastics Glow Under Black Light

Many plastics glow under black light. Often, you can tell a plastic is likely to glow just by looking at it. For example, neon-colored acrylic may contain fluorescent molecules. Other types of plastic are less obvious. Plastic water bottles usually glow blue or violet under ultraviolet light.

White Paper Glows Under Black Light

White paper is treated with fluorescent compounds to help it appear brighter and therefore whiter.

Sometimes forgery of historical documents can be detected by placing them under a black light to see whether or not they fluoresce. White paper made post-1950 contains fluorescent chemicals while older paper doesn't.

Cosmetics May Glow Under Black Light

If you bought make-up or nail polish with the intention of getting it to glow under a black light, you knew what to expect.

However, you might want to check your regular makeup too, or next time you pass a bright fluorescent light (emits UV) or black light, the effect might be more "rave party" than "office professional".

Many cosmetics contain fluorescent molecules, mainly to brighten your complexion. Usually, this just means you'll look ghostly.

If the molecule emits a color, watch out! Hint: The bars at many restaurants have black lights to make drinks look pretty. 

Fluorescent Plants and Animals

If you have a jellyfish handy, see what it looks like under a black light in a darkened room. Some of the proteins within a jellyfish are intensely fluorescent.

Corals and some fish may be fluorescent. Many fungi glow in the dark. Some flowers are 'ultraviolet' colored, which you cannot ordinarily see, but may observe when you shine a black light on them.

Other Things That Glow Under Black Light

Many more items glow when exposed to black or ultraviolet light.

Here is a list of other materials that glow:

·   Petroleum jelly, such as Vaseline, glows a bright blue color under a fluorescent light. (see a photo)

·   Uranium glass or vaseline glass

·   Rock salt

·   Fungus that causes Athlete's Foot (supposedly glows orange)

·   Turmeric (a spice)

·   Olive oil

·   Canola oil

·   Some postage stamps

·   Highlighter pens

·   Honey

·   Ketchup

·   Cotton balls

·   Pipe cleaners (chenille craft sticks) 

Anne Marie Helmenstine, Ph.D.

Ph.D. in biomedical sciences from the University of Tennessee at Knoxville - Oak Ridge National Laboratory.

Science educator with experience teaching chemistry, biology, astronomy, and physics at the high school, college, and graduate levels.

ThoughtCo and About Education chemistry expert since 2001.

Widely-published graphic artist, responsible for printable periodic tables and other illustrations used in science.

Experience

Anne Helmenstine, Ph.D. has covered chemistry for ThoughtCo and About Education since 2001, and other sciences since 2013. She taught chemistry, biology, astronomy, and physics at the high school, college, and graduate levels. She has worked as a research scientist and also abstracting and indexing diverse scientific literature for the Department of Energy.

In addition to her work as a science writer, Dr. Helmenstine currently serves as a scientific consultant, specializing in problems requiring an interdisciplinary approach. Previously, she worked as a research scientist and college professor. 

Education

Dr. Helmenstine holds a Ph.D. in biomedical sciences from the University of Tennessee at Knoxville and a B.A. in physics and mathematics with a minor in chemistry from Hastings College. In her doctoral work, Dr. Helmenstine developed ultra-sensitive chemical detection and medical diagnostic tests.

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