Homemade fluorescence

Tea, oil, and paper can glow?

Difficulty:
Danger:
Duration:
20 minutes
Homemade fluorescence

Safety

  • Carefully review the general safety advice on the back of the box cover before starting the experiment.

Step-by-step instructions

  • Tea and oil

Take your UV light and test it on liquids you have at home! You are looking for liquids that glow under UV light. Just don’t mistake reflected light for a glow—the glow will be a different color, like green, red, or white. Here’s a hint: try tea, vegetable oil, or tonic water.

Add a curious twist to your experiment with not-so-common liquids! Ask your parents if you have an antiseptic (containing at least 70% alcohol) and pour it over dried tea leaves (or crushed leaves from a teabag), then see what happens when it's exposed to your UV light. This particular mixture should emit a pink or red glow under the UV light. Compare the glow you get from ordinary brewed tea to the tea leaves with antiseptic. What other glowing liquids did you find? Warning! Do not drink the liquid you made for the experiment. It’s not tea anymore.

  • Glowing figures

This project requires darkness, so it’s best to conduct it in a windowless room or at night, maybe even under a blanket!

Take the special sheet of paper from the set and turn off the lights. Does the paper glow? It might if it was recently exposed to a bright light, but it may not. Now shine some light on it—hold it near a lamp or expose it to sunlight. If neither of these is an option, use the UV light from the set. Return the paper to the darkness once again—it should glow brighter this time! Use scissors to cut a shape out of the paper (a star, for example), and attach your DIY glowing sticker wherever you like. It will continue glowing in the dark for minutes to hours after light exposure.

Disposal

  • Dispose of solid waste together with household garbage.

Scientific description

  • Tea and oil

The effect you observed is called fluorescence, and arises because some liquids can absorb the energy of the UV light and then emit light themselves. The fluorescence stops immediately after you stop exposing the liquid to the light, and the light particles—photons—the liquid emits have less energy than the light particles it absorbs. The UV light generates photons with relatively high energies, which is why it is effective in inducing fluorescence. As they fluoresce, different molecules produce photons with different amounts of energy. This fact can be used if you want to determine the concentration of a certain substance in a mixture. For example, the composition and quality of your tea can be determined by studying the photons produced under the influence of various kinds of light. This, of course, requires sophisticated measuring tools and cannot be done with the naked eye.

With some liquids, it can be difficult to distinguish fluorescence from reflected light, so we recommend that you illuminate the liquid from an angle and look at the result from the same angle.

  • Glowing figures

Some substances can absorb light energy and glow for a long time after exposure. These materials are said to be phosphorescent, and the phenomenon itself is called phosphorescence. These substances emit the light energy they absorbed slowly, sometimes glowing for several hours. At some point, the energy they have absorbed runs out, and they stop glowing. However, you can “recharge” phosphorescent materials by re-exposing them to light.