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Walking Rainbow Experiment

Watch a rainbow walk in this cool experiment!

Age Group: Elementary

Topics: Capillary action

Difficulty: Easy to perform and see results


  • Small Clear Cups (may get stained due to food coloring - disposable cups are recommended)

  • Paper towel

  • Food coloring

  • Water


1. Place 5 cups in a line on your table

2. Add water only to the 1st, 3rd, and 5th cup.

3. Add a few drops of your food coloring to each cup, each with a different color. To make a more rainbow-like effect, place the colors in rainbow order.

4. Fold the paper towel sheets horizontally twice, so they form a column. Insert them into the cups, with one end of each paper towel is in a cup of water, and the other end into an empty cup. Keep doing this until all the cups have 2 ends of the paper towel in each (aside from the beginning and ending cups)

5. Watch the water travel across the paper towels to form a rainbow!

How It Works:

The capillary effect is a process in which liquids (like water) travel upwards through a soling which is porous or has many gaps. Paper towels are made up of small fibers with gaps. As a result, water gets pulled into these gaps because of capillary action. This allows the water to travel through the paper towel in order to form the cool rainbow you saw. This phenomenon is also seen in nature when the roots of plants like trees and flowers are able to suck water out of the ground.

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