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 ...

Add Yahoo as a preferred source to see more of our stories on Google. Need some gifts for your kids, grandkids, nieces and nephews? More specifically, gifts they won't toss aside as soon as they open ...

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 ...

Ciphers and invisible ink – many of us experimented with these when we were children. A team of Chinese scientists has now developed a clever, high-tech version of "invisible ink". As reported in the ...

Coded messages in invisible ink sound like something only found in espionage books, but in real life, they can have important security purposes. Yet, they can be cracked if their encryption is ...