-Something fun to do with your kids!
Use lemon juice, dip the back of a matchstick in the juice and write your secret message on a piece of paper.
When it dries, it becomes invisible. To make it visible, you need to hold it carefully over a candle until the secret writing appears! (A bowl of water near by could be smart. -We had a couple of accidents...)
My daughter and her friend loved the activity and have now decided that they shall start a Secret Club.