Emphasis Preaching Journal

If you have ever watched a spy movie, you likely witnessed a scene in which a secret message passed through enemy lines because it was written in invisible ink. There are quite a number of liquids that can serve as invisible ink, the most common are heat sensitive. Lemon and onion juice work best; milk and vinegar work not as well, but still work. Simply take some writing instrument, dip it in the "invisible ink," and write your message. When the recipient of the message holds the paper with the message over a candle or a light bulb ... presto! The juice darkens and the message appears.