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Glow in the Dark Experiments

Glow in the Dark Experiments

I did this program during our winter break "Geek Girl Day" (grades 3-5) and for preschool kids (ages 3-6 with their parents) over spring break in April.


First, you will need a dark space (preferably with no windows) and several black lights. We ran this program in the library's basement and used three large blacklights that we suspended from the ceiling using zip ties. Depending on your space, you might also need two tables, garbage bags, a water cooler w/ water, and a chalkboard/whiteboard.



  • Tonic water*

  • Seltzer

  • Bank notes ($10*, $1)

  • Baby oil

  • Toothpaste*

  • Wet wipes

  • Highlighters*

  • Petroleum jelly*

  • Laundry detergent*


  • Petroleum jelly*

  • Wet wipes


  • Highlighters*

  • Pliers

  • Cups of water


  • Black paper

  • Paint brushes

  • Water (to clean brushes)

  • Laundry detergent*

*items should glow under black lights.


  • Once we got down to the basement, I started off by asking the kids: Have you ever seen something that glows in the dark? What makes it glow? Since we were in our library's basement where our booksale is, I hid the answers on slips of paper that I stuck in books whose covers glowed under the black lights. I told the kids that the answer to my question was hidden in the room somewhere, and encouraged them to try and find it. Of couse, I had not yet turned the black lights on, so they couldn't find it, and after a few minutes I called them back.

  • Then I asked: Do you know what a blacklight is?

  • Explanation: An ultraviolet (UV) lamp or “blacklight” shines ultraviolet light. This is a type of high-energy light that is invisible to the human eye. However, it makes some substances glow with a light you can see.

  • I had spread the items from the HYPOTHESIS ACTIVITY materials list out on the table. Together we identified each item and then hypothesized about which things on the table (and around the room) would glow. We recorded each guess on the white board.

  • Next I turned the lights off and the black lights on. The kids were so excited! I reminded them to make observations. What things glow and why? We went through each item on the table to see if our predictions had been correct. I also asked the kids to take another look around the room to see if they could find the hidden answer in the books, now. Eventually someone did, and I asked that child to read the explanation printed on the paper.

  • The ultra violet (UV) light coming from your black light lamp excites things called phosphors. Tonic water and the dye from highlighter pens contain phosphors that turn UV light (light we can’t see) into visible light (light we can see), which is why these items glow in the dark when you shine a black light on them.

  • We very briefly discussed what other kinds of things black lights might be used for, before doing three activities using our glow in the dark substances.

  • Black lights are used in forensic science, artistic performances, photography, authentication of banknotes and antiques, and in many other areas.

  • PETROLEUM JELLY: Will this glow? Try it on your skin and other surfaces (floor, wall, paper, etc.) Turn the lights out and make observations. Don't forget to wipe everything clean.

  • HIGHLIGHTER Experiment: Give each kid pliers, a highlighter, and a cup of water. Show them how to pull the back out and squeeze the tube of highlighter "ink" into the cup of water. Then turn lights out and the black lights on!

  • Which one glows the most brightly? What happens if we mix different colors together?

  • LAUNDRY DETERGENT: Give each kid a paint brush and let them “paint” with laundry detergent. First in the light, then in the dark.

  • I also try to ask questions throughout each activity to maximize the learning opportunities: Does anyone remember why this works? What is a black light? What particle does it excite via radiation?

Detailed explanation: (This is what I hid in the books.)

Black light (also known as UV or ultra violet light) is a part of the electromagnetic spectrum. The electromagnetic spectrum also includes infrared, X-rays, visible light (what the human eye can see) and other types of electromagnetic radiation. A black light lamp such as the one you used emits a UV light that can illuminate objects and materials that contain phosphors. Phosphors are special substances that emit light (luminescence) when excited by radiation. Your liquid glowed under the black light because it contained phosphors. If you used a highlighter pen then the UV light reacted with phosphors in the dye. If you used tonic water then the UV light reacted with phosphors in a chemical used in tonic water called quinine. Toothpaste and laundry detergent often contain phosphors in order to make whites look brighter. Remember, there are UV rays in natural light too!

There are different types of luminescence, they include fluorescence (used in this experiment, it glows only when the black light is on), phosphorescence (similar to fluorescence but with a glow that can last even after the black light is turned off), chemiluminescence (used to create glow sticks), bioluminescence (from living organisms) and many others.

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Stephanie C. Prato

is the Director of Play to Learn Services at the Fayetteville Free Library in New York. 

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