Age range: 8-18
Prep Time: 5 min
Learning Time: 5-10 min
Estimated Material Cost: $1-5

Have you ever wanted to write a secret message that only your friends would be able to read? Using some materials that you already have at home; you can do just that! Let’s use some science of water to create our own colorful secret message.

Materials:

• Thick piece of white paper (cardstock or watercolor)
• White crayon
• Washable markers
• Paintbrush
• Water

Step-by-step Instructions:

Follow the instructions written here or check out our video instructions .

1. Write your message onto the piece of water with your white crayon. It should be almost impossible to see or read.
2. Take a washable marker and scribble some lines over your message. Repeat this process until your paper is covered in a couple of different colors. All you should see on the paper right now are the marker scribbles.

3. To reveal your secret message, dip your paintbrush into some water and move the wet paintbrush across the page.

4. Make observations as the markers begin to mix and your message is revealed!

What’s happening?

Some materials, like a sponge, absorb water. Other materials repel water. That means that water will not stick to it or be absorbed by it. The wax in the crayon is hydrophobic (water-fearing), meaning that it will repel any water that it comes into contact with. The water will have a very hard time washing that crayon off the paper. The markers, on the other hand, will easily start to wash away and mix when water is put onto the paper. As the marker is washed away, the hydrophobic crayon is revealed underneath and our message can be read!

Explore further!

Do you think any other materials are hydrophobic and will repel the water? Try writing your message in some other materials and observe what happens when they get wet. You might try:

• Chalk
• Pen
• Highlighter

Can you think of any materials we use everyday that are hydrophobic? What do you use whenever it rains to keep you dry?

Check out our other activities!