Britannica Sources used in this answer

How does a glow stick create light after it is bent?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

time-lapse photo of fireflies — Bioluminescence Time-lapse image of fireflies in the Catskill Mountains, New York. Firefly light is a cold light, with approximately 100 percent of the energy given off as light and only a minute amount as heat. Only light in the visible spectrum is emitted.

A glow stick does not rely on bioluminescence, which is a specific type of light emission found in living organisms like fireflies and bacteria. Instead, a glow stick functions through a process called chemiluminescence.

When you bend a glow stick, you snap an internal glass tube that separates two chemical components. This action allows an oxidizing agent, typically hydrogen peroxide, to mix with an oxalic acid ester. This mixture creates a high-energy intermediate molecule that transfers its excitation energy to a fluorescent dye (a fluorophore). As the excited dye returns to its ground state, it releases this energy as visible light, causing the stick to glow.1

This reaction is a form of indirect chemiluminescence, where the energy from the initial chemical reaction is transferred to a secondary molecule that emits the light.1