An infrared light that makes a stamp on a the hand visible

[partialfracti]

I read about a type of identification system in which a person's hand is stamped with some sort of ink or substance that is invisible to the naked eye. This normally invisible stamp on the human hand is visible under an infrared light. I remember that an infrared camera sees things that give off heat. Apparently infrared radiation is heat radiation.

I don't think the stamp makes the hand hotter. How would the invisible stamp on the human hand be made visible by infrared light?

 

[turbo]

Are you certain that is is not ultraviolet light? Such stamps/scanners have been around for at least 40 years.

 

[partialfracti]

Perhaps what I read about is ultraviolet light.