Your students can't see ultraviolet rays, but they'll know they're there with these special craft beads. Have your class make bracelets or necklaces while the beads are white, and then wear them outside. When they see that the ultraviolet-sensitive pigment changes colors, even on a cloudy day, your young scientists will understand that UV light is around them, even when they can't see it. The beads will revert back to white when they are no longer exposed to UV rays and will change over and over again without fading for use in many cool science experiments. Includes approximately 500 beads. Choose your color.