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Chemistry / Looking for ink or paper that changes color or appears/disappears after 2 hours.
« on: 07/04/2009 18:43:48 »
I am trying to find a chemical or ink that will show up or disappear after 2 hours. I would like this to activate with exposure to oxygen or, possibly, through a chemical reaction. The key is to have a non-toxic way to indicate that 2 hours has passed and to be able to display this on paper or other material. Any thoughts are appreciated.