BRIDGEPORT, W. Va. (WDTV) - Have you ever wanted to write an invisible message to a friend that only they knew how to read? Well, all you need is some water, lemon juice, a Q-tip, a blank paper, and a source of heat. You can use a lighter or a candle but always have parental supervision when working with fire.
All you have to do is put some lemon juice in a cup and add a few drops of water. Mix it up with your Q-tip. Then with that same damp end of your Q-tip, write your secret message. Once your paper is dry, you can give the message to a friend. The way your friend is going to reveal it is by applying heat to the paper.
Why does the heat reveal your message? Well, the lemon juice is an organic substance and contains carbon compounds. The heat added breaks down the compounds and releases the carbon. When the carbon came in contact with the oxygen in the air, it oxidizes and the lemon juice turns light or dark brown.
You don't need heat to make oxidation to occur. Some fruit themselves can turn brown from oxidation. Ever leave an apple slice out in the open too long? It turns brown because of oxidation.