How long a glow stick will glow depends on the age, color, size and temperature of the glow stick. A glow stick typically contains fluorescent dye and several chemicals separated by a delicate vial. When you bend the glow stick, the vial breaks and the chemicals combine, releasing photons so that it glows. It will continue to glow until the chemicals are completely used up.
Cooler Temperatures Help Glow Sticks Last
Keeping a glow stick cool will help it glow longer. The chemical reaction in the stick will slow at cooler temperatures, so the stick will glow for a longer period of time. However, cold will also decrease the brightness of the glow. You'll get more time out of the glow stick overall, but less intensity.
You can also store a glow stick in the freezer during the day to slow the reaction to almost nothing. Then when it gets dark, run the tap on warm and hold the glow stick under the water to warm it up until it starts glowing again. Some glow sticks can last a few nights by storing them in the freezer during daylight hours. However, do not thaw frozen glow sticks in the microwave, as they do contain hazardous chemicals.
Some Colors Glow Better Than Others
For a really long-lasting glow, choose a green or yellow glow stick. The fluorescent dyes used in these glow sticks tend to have the most staying power. Blue and purple glow sticks will also glow brightly, but they will not last as long as the chemical reaction takes place more quickly. Purple, in particular, will have a shorter lifespan.
Bigger Glow Sticks Last Longer
If you need a glow stick to last for a long time, choose a bigger one. The chemical reaction will continue longer because there are more chemicals contained in large glow sticks to react. The larger the glow stick is, the longer it will glow.
Age and Storage Also Affect Glow Time
Newer glow sticks will inherently glow longer as the chemicals are fresher. Glow sticks typically have a shelf life of one to five years depending on the size and brand. But the older the glow stick is, the less time it will glow. Most glow sticks will have an expiration date printed on the outer packaging, but not the glow stick itself. Expired glow sticks are still safe for use and will glow, but the light will be noticeably dimmer.
How the glow stick was stored can also affect overall glow time. Glow sticks should be kept in the dark in a cool and dry place. If the sticks are exposed to humidity or sunlight, the chemicals can degrade, resulting in a shorter glow time.