The magic of glow in the dark paper lies in a special group of chemicals called phosphors. These phosphors are charged when exposed to light, through a chemical process called radioluminescence. Once the light is turned off, they emit that charge in the form of their own light – which causes that eerie greenish glow. The glow usually lasts a very long time, so you can be confident that your glow in the dark Halloween wall art will last through the night.