From the website:
Voltage does not rely on UV, neon or black lights to create glow. Instead, it produces its own light! Tiny, microscopic particles in the gel come together in the mixing process to produce a bright colorful glow that can be seen in partial light and in the dark for at least 6-8 hours (technically, this incredible effect lasts more than 24 hours at a diminishing glow). The glow is bright enough to even use in lieu of a flashlight to go through a campground at night!
Link - via Presurfer