Wikijunior:Big Book of Fun Science Experiments/Secret Messages

Have you ever wanted to write a secret message where nobody could look in except you and the person you are writing to because it is invisible to all? If you do we can tell you how...

You Will Need

 * A piece of paper
 * A paintbrush
 * Half a lemon
 * A small dish

Method

 * Squeeze the half lemon over the dish so the juice drops into a bowl
 * Dip the paintbrush in the juice and write your message on the paper

You Will Need

 * An oven

Method

 * Gently heat the oven to a warm temperature
 * Put your piece of paper in the oven & when the lemon juice turns brown, take your paper out of the oven and read the message!

Principle
Lemon juice, and any other things made from plants, are called organic chemicals and contain carbon. When organic chemicals burn the carbon, which is black, breaks off from the molecule, like wood turns black when it is burned. Instead of lemon juice, you could use any fruit juice or tree sap (don't cut a living tree to get the sap), but this experiment works best with colourless or light-coloured liquids.