Surely this one is straight out of the movies or some superhero comic book? You would certainly think so, but this highly effective spray can turn opaque paper temporarily translucent, allowing you to view the contents of an envelope without ever actually opening it. Thirty seconds later, the envelope will return to it’s original state, leaving no marks, discoloring or indeed any other indications that it may have been tampered with (left image)
Another spray - Clue spray - is designed to leave an invisible film on any surface, which when touched, is transferred to a person’s hand or clothing. Looking for clues or a suspect? Then look no further. Unknown to the victim, the spray remains for up to five days, even if the hands, for example, are washed repeatedly. The spray can’t be seen by the naked eye, but shows up as fluorescent under ultra-violet light (right image)
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