

Luminous band-aids

Last night after bedtime Katara asked for a small band-aid for her knee. I went into the bathroom to get one, and unwrapped it in the dark. The band-aid itself is circular, about 1.5 cm in diameter. It is sealed between two pieces of paper, each about an inch square, that have been glued together along the four pairs of edges. There is a flap at one edge that you pull, and then you can peel the two glued-together pieces of paper apart to get the band-aid out. As I peeled apart the two pieces of paper in the dark, there was a thin luminous greenish line running along the inside of the wrapper at the place the papers were being pulled away from each other. The line moved downward following the topmost point of contact between the papers as I pulled the papers apart. It was clearly visible in the dark. I've never heard of anything like this; the closest I can think of is the thing about how wintergreen Life Savers glow in the dark when you crush them. My best guess is that it's a static discharge, but I don't know. I don't have pictures of the phenomenon itself, and I'm not likely to be able to get any. But the band-aids look like this: Have any of my Gentle Readers seen anything like this before? A cursory Internet search has revealed nothing of value. [ Addendum 20180911: The phenomenon is well-known; it is called triboluminescence. Thanks to everyone who has written in over the years to let me know about this. In particular, thanks to Steve Dommett, who wrote to point out that, if done in a vacuum, triboluminescence can produce enough high-energy x-rays to image a person's finger bones! ]

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