Climbing Rainbow Science Experiment For Kids

We had a day at home a few weeks ago and I knew it was the perfect time to try this climbing rainbow science experiment. With just a few common household items we created rainbow magic again, and again, and again (I actually think we did this activity 7 times because my little one loved it so much!). See my full instructions as well as things we learned to do (and not to do) to create a fun water walking experiment below.

rainbow going into cups with water mixing in the water

This fun science experiment is a great way to introduce capillary action to your kids. It was a fun visualization for my boys to see how the water was absorbed through the paper towel and the colors traveled up the paper towel as it was exposed to water. This was a great lesson in cause and effect and gave us an opportunity to talk about the scientific process of this activity (more on this below). 


  • Absorbant paper towels
  • Markers (you can choose all different colors but we did the colors of the rainbow!)
  • 2 empty cups
  • Water
  • Clothes Pin
rainbow paper towel with marker on ends

How To Create Your Own Climbing Rainbow Science Experiment

  1. Take your strip of paper towel and cut it into a rainbow shape
  2. Use your markers to make color blocks from the bottom of the rainbow and up about 1″-2″ depending on the size of your rainbow
  3. Take your clothes pin and clip it to the top of the paper towel rainbow
  4. Fill your two empty cups with water, I would pour the water until the cups are about half full
  5. Put your rainbow ends into the cup holding the rainbow up by the clothes pin
  6. Watch the water climb up the paper towel, allowing the colors to climb and secondary colors to form
  7. Enjoy your fun beautiful rainbow!
child sitting at table clipping clothes pin on top of rainbow

Tips/Tricks When Doing The Climbing Rainbow Experiment

Like I mentioned earlier, we did this experiment A LOT of times because my kids were just mesmerized by the entire process. With all of those trials we learned a lot and I wanted to pass along some tips:

  • The more absorbent the paper towel the better your colors will climb
  • I would recommend primary colors when you color on the paper towel strip, they seem to show better & keep their color as the water moves the color up the paper towel
  • Don’t be shy on the amount of marker ink you add to the paper towel, our best results were when my 4 year old spent a lot of time coloring in one spot 🙂
  • Fill your cups with warm water, when we did this it seemed like the colors climbed easier
  • Allow your colors to dry before putting them into the cup, if you do it when the paper towel is still wet from the marker the colors seem to just disappear into the water and you end up with some really cool colored water- see photo below
paper towel in 2 cups of water to see the climbing rainbow experiment

Questions To Have Your Little Scientists Consider Before This Experiment 

This is such a fun, easy science experiment that honestly kids of all ages would enjoy. I loved that it was so simple and we had all of the materials at home. Plus, clean up was quick (an extra bonus point in my book).

There are a lot of different ways to pull in some fun learning opportunities with this experiment. Here are some questions you could ask your child before you do the experiment. Have them write down their answers and then see how close they were as they do the rainbow paper towel experiment.

  1. Will the water walk all the way to the top of the rainbow?
  2. How long will it take for the colors on each side of the rainbow to meet?
  3. Is there a difference with different brands of paper towels?
  4. Does the color climb with different liquids or just when it is put in water?
  5. Would the colors climb differently if the water level in the cups changed?
rainbow colored above 2 cups

What Is Capillary Action?

Capillary action is when a liquid moves through or along another material despite an opposing force. For this experiment that opposing force is gravity. A great example of this is when water is taken from plant’s roots and is brought up through the plant stem to the leaves and flowers.  The way the water travels through the plant, despite the opposing force of gravity, is just like how the colors move up the paper towel in this experiment. 

completed rainbow experiment for kids on table

Other Great Science Experiments For Your Kids

  • This walking water experiment is another favorite in our house (tutorial is coming soon!)
  • These giant bubbles are so fun to make and play with all summer long
  • This colorful fizzing sensory bin from My Bored Toddler is on our list to try this summer

I would love to hear from you if you do this experiment with your little scientists!

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