“How to Send Secret Messages,” Friend, Sept. 1990, 11
Here’s a sure way to send a secret message to a friend:
Dip a sheet of blank paper into water, then place the wet paper on a smooth, hard surface, such as a window or mirror.
Cover it with a dry sheet of paper.
Pressing firmly with a hard lead pencil, write your secret message on the dry sheet.
Throw away the dry sheet. Your message will be cleary visible on the wet sheet but will disappear as the sheet dries.
When your friend gets the paper and dips it into water, the message will reappear!