Retorts

Triboluminescence?

Not everyone opens their mail in the dark, but recently I chanced to do so. Coming home late, and before turning on the power, I began pulling the flap of an envelope which was of the seal-easy or self-adhesive kind, when behold, there was a distinct flash. No, it did not come from a passing car, and the mail itself was innocent enough (a bank statement as a matter of fact), but the observation was genuine. Since then I have tried opening other envelopes this way and found that a faint bluish light is produced along the seal as the adhesive faces come apart on a sudden pull.

So, what is the explanation? Are further experiments required? Can other people confirm it? Does standing on a nylon carpet or stroking the cat have anything to do with it? Is the Auckland climate a factor? If a chemical reaction is involved, have the kinetics of the letter (Fastpost or Standard) to be taken into account -- or in other words, does it matter how long the envelope has been sealed?

May I invite readers, whether traditional or constructivist in outlook, to take up this matter.

Michael Taylor, Department of Chemistry, University of Auckland

We contacted stationery manufacturers Croxley, and after they had been convinced that no, we weren't pulling their leg, and yes, it does work as you said, they sent an enquiry to their adhesive manufacturer. We'll keep you posted.