Do you ever need to tell your friends messages, but can’t risk other spies figuring out your secrets?
Then you need to practice writing with lemon juice! Wait, what? It’s true, lemons are a spy’s best friend.
What you need:
- Lemon (or an orange or milk)
- Q-Tip or cotton swab
- White paper
Squeeze the lemon over a bowl so you have collected its juice. Add a few drops of water and mix. Dip your Q-Tip in the mixture and then write your message on the paper. Wait for it to dry, then have a friend hold the paper near a light source, like a lamp. The message will appear!
Lemon juice oxidizes (it has a reaction with oxygen) and turns brown when heated. The message is revealed with light because the lemon juice becomes hot enough to change color and is then visible to the eye. Just don’t get it IN your eye!