Glow-in-the-dark materials utilise substances called phosphors in order to softly emit light after being charged. Common glow-in-the-dark materials can be charged by energy from the visible light part of the electromagnetic spectrum. Technically, you could have a phosphor that could be charged by UV, Infra-red or even X-rays. After being charged by visible light, the phosphor released energy in the form of light to give a soft, luminescent glow. The length of time that a phosphor will glow after being charged is called the persistence. Zinc sulphide and calcium sulphide are commonly used phosphors.

Glow-in-the-dark filaments are usually made by combining a phosphor or phosphor-like substance with a plastic resin, commonly PLA or ABS. In general, glow-in-the-dark filaments will print similarly to the carrier polymer that has been used although there may be some differences so always check the Technical Data Sheet.