Why do wintergreen Life Savers spark when crunched?

Dear Cecil:

During a lull at one of our recent staff meetings, I questioned my boss, brother, and dentist (one and the same, although not necessarily in that order of importance) about the mysterious properties of Life Savers candy. I'd heard that the wintergreen and peppermint varieties, if crunched smartly between the teeth, will emit a cloud of blue sparks. My brother verified this phenomenon, based on his own childhood experiences, but was at a loss to explain just how and why it occurs. Any ideas?

Cecil replies:

Dear Dona:

It is all very well for a layman to take her brother’s word on things like this, Dona, but professionals such as myself insist on checking out the situation firsthand. Accordingly, I have conducted a rigorous program of experiments, aided by the Straight Dope Kamikaze Research ("we laugh at death") & Display Advertising Battalion, which will do anything if it will get them out of actually having to work for an hour.

Having completed our labors, we have arrived at the following conclusions: (1) wintergreen Life Savers will indeed produce spectacular if somewhat pint-sized clouds of blue flame when mashed vigorously between the molars. However, (2) peppermints don’t do squat.

Our failure in the latter department may perhaps be attributed to the fact that the peppermint Life Savers we had on hand were unbelievably ancient, and had consequently absorbed considerable moisture, which is said to inhibit sparking. However, theoretical considerations lead us to believe that even under the most favorable conditions the sparks from the peppermints would not be very bright.

Most students of the modern Life Saver classify sparking as a type of triboluminescence, which occurs when something is crushed or torn, the something in this case being the hard crystalline sugar that Life Savers contain. (Another example of TL is the spark you get when you tear the piece of tape off the end of a roll of photographic film.)

Wintergreen sparking, it’s believed, is actually a three-step process. Step One: When you shatter the sugar crystals with your teeth, electrons (which are negatively charged) break free. As a result, the atoms in which the electrons were formerly embedded become positively charged. In what amounts to a subatomic game of musical chairs, the free electrons dash around madly trying to find a new home.

Step Two: Meanwhile, as the sugar crystals disintegrate, nitrogen molecules from the air attach themselves to the fractured surfaces. When the free electrons strike the nitrogen molecules, they cause the latter to emit invisible ultraviolet radiation, along with a faint visible glow.

Step Three: The UV radiation is absorbed by the wintergreen flavoring, methyl salicylate. This then emits the fairly bright blue light you see. Pretty complicated, I admit. Clearly the planners in the Pentagon weren’t the first to be obsessed with high-tech gimcracks.

I should point out that even without the wintergreen flavoring, virtually all crystal sugar candy, including peppermint Life Savers, will emit some visible light when crushed, although it’s usually pretty faint. The effect was first described in 17th-century Italy, and since then it’s been discussed in numerous papers and articles.

Some of these are more imaginative than others. For instance, I have here an unpublished paper by researcher Patricia Nakache that is somewhat grandly entitled, "The Life Saver: A New Energy Source?" It contains the fascinating news that if you connect a Life Saver to a neon tube with wires and bash it (the Life Saver) with a hammer, the neon tube will flash. We can thus envision that when the next energy crunch comes, an adequate supply of Life Savers will be as important to survival as MasterCard is today. Better hustle on down to the store toot sweet.

Send questions to Cecil via cecil@straightdope.com.

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