Top Secret Invisible Ink

Materials:

• Toothpick
• Lemon juice
• Paper
• Heat source
• Vinegar or milk

Procedure:

1. Dip the tip of a toothpick into lemon juice
2. Then use it to write a secret message on a piece of paper
3. Use lots of lemon juice for each letter you write
4. Allow the paper to dry until you can’t see the writing anymore
5. Now move the paper back and forth over a heat source, such as a lightbulb or iron
6. As the ink gets warm, your message is revealed!

Explanation:

The acid in the lemon juice breaks down the cellulose of the paper into sugars. The heat supplied tens to caramelize the sugars, making them brown and revealing the secret writing. Repeat this with vinegar or milk to find out which makes the best invisible ink!

Source: 1001 Ways to Explore Science and Nature