Perhaps you've seen glow sticks adding a fun light to a Halloween costume or the same glow in necklace or bracelet form at a party. Glow sticks are typically a plastic cylinder about four or five inches (10 to 13 cm) long and less than an inch (2.5 cm) in diameter. Wearable glow products are made of a more flexible plastic and take on many shapes.

No matter what their form, glow sticks depend on a chemical process known as chemiluminesence to produce their light. In chemiluminesence, a chemical reaction causes a release of energy. Electrons in the chemicals become excited and rise to a higher energy level. When the electrons drop back to normal levels, they produce energy in the form of light.

The chemicals used to create this reaction in glow sticks are usually hydrogen peroxide and a mixture of phenyl oxalate ester and the fluorescent dye that gives the glow stick its color. The hydrogen peroxide is contained in a small glass tube that floats within the mixture inside the plastic glow stick. This is why you must bend a glow stick to make it start glowing. When the stick bends, the glass vial breaks, the hydrogen peroxide is released, the chemical reaction begins and you get the distinctive glow.

The duration of your glow stick's glow will vary depending upon the exact composition and quality of the chemicals inside. You may have heard that you can preserve your glow stick by sticking it in the freezer. Indeed, cooling a glow stick will slow down the chemical reaction taking place inside. The glow won't be as bright, but it will be spread out over several hours. Conversely, you can also heat a light stick to speed up the chemical reaction. This will produce a much brighter light, but it won't last nearly as long because the reaction will use up all of the available hydrogen peroxide much more quickly.