Buzz
If you grew up in the 80s or 90s, your house was probably full of glow-in-the-dark items. Yo-yos, stickers, action figures, clothing—you name it. As a kid, I thought they were almost magical. As an adult, the effect isn’t as awe-inspiring, but the science behind it is still fascinating.
Glow-in-the-dark objects owe their glow to a substance called a phosphor, which belongs to a group of materials that emit visible light after being energized. Some phosphors occur naturally, like those in your teeth and nails, while chemists have developed many others. The most commonly used phosphors for glow-in-the-dark items are those that can absorb regular light and emit a lasting glow.
To create a glow-in-the-dark item, you mix a suitable phosphor with plastic, and voilà, you have a glowing object. When exposed to sunlight or light from a lamp, the phosphors in the plastic absorb the energy, and once the lights are off, the phosphors slowly release that energy as a faint glow.
In addition to the typical glow-in-the-dark objects, there are some special cases where the glow works differently. Glow sticks, for example, produce light through chemiluminescence, where light results from a chemical reaction. Items like clock or watch hands that glow for hours after the light is turned off function via radioluminescence. These timepieces use phosphors along with a small amount of a radioactive element, such as radium, which emits tiny amounts of energy (harmless to users but historically problematic for manufacturers) to keep the phosphors continuously energized and glowing throughout the night.
* Phosphors were more than just the magic behind my glowing toys; they were also responsible for creating the images on the screens of the old computers at my grade school. In fact, you can thank them for your first experience with Oregon Trail.
