Did you know you could use the juice from a lemon to write a secret message? Materials: Instructions: STEP 1: Squeeze the lemon juice into the plate. STEP 2: Dip the cotton swab into the lemon juice.

When I was a kid, my friend had this pen with invisible ink. You could write a note with it and then the person you sent it to had a different pen that made the text show up. We though it was awesome ...

Add Yahoo as a preferred source to see more of our stories on Google. William Abel, a mail censor at Iowa's State Prison, Fort Madison, using a hot iron to bring out a secret message written in lemon ...

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 ...