Have you ever wanted to send a Valentine that feels like a spy note? With a few simple ingredients, you can write a hidden message that appears like magic! Have fun while learning the real science behind it.
Here’s what you’ll need:
- lemon juice (or milk),
- cotton swabs or a paintbrush,
- white paper,
- a heat source (hair dryer used by an adult, a lightbulb that puts off a lot of heat)
Steps:
1) Write a message with lemon juice using a swab. It can be “You’re awesome”, “Best friends”, or even hidden clues for a scavenger hunt!
2) Let it dry completely. To make it even more secret, you can write or doodle on the paper (carefully, after it fully dries!)
3) Ask an adult to gently warm the paper (hair dryer works well). The message will darken and appear!
How does it work?
Lemon juice and milk contain natural compounds that are mostly invisible when they dry. When you apply heat, those compounds break, releasing carbon. In contact with the air, the substance oxidizes, turning brown faster than the surrounding paper. That’s why the writing changes color and suddenly becomes visible!