LUMINESCENCE

  
Around Halloween, stores begin to sell necklaces, wands and other plastic items that glow coolly in the dark. Based on bioluminescence, they contain luciferins, and work the same way as a firefly’s glow. But, for extra sparkle, a trick or treater might also chew wintergreen Lifesavers. If you stand in the dark and crush one between your teeth, it will spill blue-green flashes of light. Certain substances (some quartzes and mica, even adhesive tape, when it is yanked off specific surfaces) are triboluminescent; they give off light if you rub, crush, or break them. Broken wintergreen fluoresces and broken sugar gives off ultraviolet light; the combination – in candies that contain both sugar and oil of wintergreen – produces tiny bolts of blue-green lightning. Try this parlor game: Step into a closet with a mouthful of wintergreen lifesavers and a friend and wait for sparks to fly.

-- Diane Ackerman, A Natural History of the Senses