What Causes Wint-O-Green Candies To “Spark” In Your Mouth?
Wint-O-Green candies, a minty offering from the LifeSaver company, will often spark and glow when rapidly crushed. By what mechanism does a tasty candy turn into a sparkler?
You can thank the phenomenon of triboluminesence for the fireworks show in your mouth. Triboluminesence is an optical phenomenon by which light is generated when material is ripped, crushed, rubbed, or pulled apart through the breaking of chemical bonds in the source material. The most common place people see triboluminesence, thanks to the popularity of this trick among school children, is the open-mouth chomping of LifeSaver’s Wint-O-Green candies.
When you crush sugar crystals, the shattering of the crystalline structure frees up electrons. These electrons in turn collide with atoms in the air around them and generate light energy. The majority of this light energy is in the ultraviolet spectrum and invisible to the human eye–you could smash rocky candy with a hammer all day long and never see so much as a spark. This is where the particular properties of the Wint-O-Green candy come into play and turn the invisible, visible.
The principle flavoring agent in Wint-O-Green candy is methyl salicylate (wintergreen oil). Methyl salicylate acts as a phosphor and, when the ultra-violet rays comes shooting out of the crushed sugar crystals, it absorbs the rays and converts them to blue light. When you smash a bunch of winter green candies in your mouth and blue sparks seem to fly about what you’re actually seeing is the ultra-violet light from the fracturing of the sugar crystals lighting up the wintergreen oil.
Other examples of triboluminesence include: under the right conditions diamonds will glow red or blue when rubbed rapidly (as they are in the cutting and shaping process), quartz crystals will create bursts of white light when rattled against each other, and certain Band-Aid wrappers and brands of tape will emit a soft glow if quickly unwrapped or snapped off the roll of tape.