Watch Capillary Action In Action with Our Walking Water Rainbow Activity
By Arlington Parks & Recreation
Posted on April 09, 2020, April 09, 2020

Even though kids are out of school right now, they can still learn a lot about science right from home with a little creativity! This walking water rainbow activity is a fun way to learn about capillary action, which is the ability of a liquid to flow against gravity in narrow spaces. This is the same process that allows water to flow from a plant’s roots to the leaves in the treetops! In this colorful experiment, you can make water defy gravity and “walk” up the paper towels to create a beautiful rainbow effect. This is also a fun way to learn about how colors mix together.

Here’s what you will need:

  • 6 small cups or jars (preferably clear)
  • Red, yellow, and blue food coloring
  • 6 white napkins (preferably a roll, but any shape will work)
  • Color Mixing Activity Sheet

First, fill three of your cups or jars with water. They should be about ¾ full for the best results.

Fold your 6 napkins into strips that are about one inch wide, and long enough to reach from the inside of one cup to another. If you have a roll of napkins this will be easier, but you can use any size or type of napkins.

Then, add 5-6 drops of food coloring to the 3 cups of water and stir with a skewer or spoon. You should have one cup of each color (red, yellow, and blue) and the colors should be strong.

Arrange all 6 cups in a circle with an empty cup between each cup of color. Place your napkin strips into the cups, and make sure they reach from inside one cup into the adjacent cup.

Watch the water “walk” before your eyes! After just a few minutes pass, the water will begin traveling up the paper towel strips. After a few hours, the water will move from the filled cups into the empty cups, and the primary colors will mix together to create secondary colors. A beautiful rainbow will form on your paper towels!

If you aren’t seeing initial results after a few minutes, try adding a bit more water and food coloring to your colored water cups. The primary colors won’t begin to mix for a few hours, so it’s recommended that you leave it for a few hours or overnight for best results.

After your rainbow has formed, you can use our coloring record sheet to track how your colors mixed together in the experiment. Click through the slideshow to find the sheet along with photos of all the steps to this experiment.

And there you have it! You just created capillary action in your own home, while also observing a cool visual effect in the process. We hope you enjoy this experiment and try it yourself! We would love to see what your rainbow looks like, so please tag us on social media @arlingtonparks and use #NaturallyFun to share your results.

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