Thursday, April 07, 2005

Thermachromic postage stamps

I got a letter from the UK in this morning's post. One of the postage stamps bore the instructions "RUB FEZZES WITH YOUR FINGER TO FIND PYRAMID". I just had to find out more.

According to the Royal Mail, this is one in a long line of trick stamps.

It uses body temperature thermachromic ink which becomes transparent when heated to body temperature.

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