How do glow in the dark things work?
Between star-shaped stickers and green-tinted tee shirts, glow in the dark things are everywhere. How is it that they absorb the light? What is this chemical?
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Answers ( 1 )
The Bad Old Days
In the past, glow in the dark paints used radioluminescence, relying on radioisotopes to store and release light. They contained radium in order to create a glow, and they also would emit alpha, beta and gamma radiation! The stories of the horrible health effects on the women who worked for the United States Radium Company in the 2920s are not for the faint of heart.
Today’s Safer Glow
Today phosphorescent chemicals are used which are non-toxic and not radioactive. They absorb visible and ultraviolet light quickly, temporarily trap the energy then emit visible light much more slowly. Some chemicals charge more quickly than others, and ultraviolet light charges all such chemicals faster than visible light. These pigments may be added to plastisol printing inks, acrylic fabric paints, resins, or any number of different polymers.
Strontium aluminate is more expensive and releases light for a longer time than zinc sulphide (doped with copper) so you’ll find it used in higher quality products. Europium and dysprosium (the non-radioactive isotopes) may be added to strontium aluminate to increase light production, but they also increase the price of the pigments.
Companies that make pigments which give off colors aside from the standard yellow-green light add fine particles of various chemicals (such as manganese or bismuth) that bind to the phosphorescent molecules and fluoresce, in essence tinting the light being emitted.
Other Ways that Things Glow
Light sticks use chemiluminescence which is a chemical reaction that releases light as a byproduct.
Bioluminescence occurs within living creatures (glow eorms, fireflies and a variety of aquatic life) similarly using a chemical reaction within their bodies to create light