A letter from the Revolutionary War with lines written in invisible ink. Credit: Wikimedia Commons Last year, the US Central Intelligence Agency released documents detailing recipes for invisible ink ...

AUGUSTA, Ga. (WRDW/WAGT) - When we were kids, “invisible ink” meant lemon juice on notebook paper, write the message, and to see it someone would have to hold it up to the light for the words to ...

A Japanese student aced an assignment on ninja culture by making her own invisible ink from soybeans in a stealthy move that impressed her professor. Eimi Haga, a member of Mie University’s ninja club ...