STEM Activity: The romping rainbow

What could be more fun than to help your preschooler make their very own rainbow? This simple experiment is part STEM (Science, Technology, Engineering and Math), and part STEAM (with Art added in).

For weeks, Bryn’s endless questions have focused on “what color does that make?” It doesn’t matter what two colors, she has to KNOW right NOW. Again and again. Oftentimes, my answer is brown. What color does red and green make? Brown. What about purple and orange? Brown. Or red and orange? Uhh, an orangey-red? Coral? I don’t know exactly what you’d call it.

We have done several color-mixing activities using various paints, but the pigments can be tough to work with sometimes to get predictable results. Blue and red, for instance, might make more of a blue-ish color than a real purple. It’s frustrating when I want to show Bryn how blue and red make purple, her favorite color, and it doesn’t exactly work out!

We decided to do a Romping Rainbow experiment, and it was super simple but still had that preschool WOW factor. I hope you try it and have fun learning as much as we did!

Here is your item list:

  • Six small clear glasses or cups. We used mason jars because it’s what we had on hand.
  • Food coloring: red, yellow and blue
  • Paper towels or sturdy toilet tissue
  • Water and a pitcher for your preschooler to practice pouring

Simple, right?

The first thing you do is arrange your glasses or jars into a pretty tight circle. Don’t make a straight line or you will miss out on one of the key colors of the rainbow. Fill every other class with water approximately one inch from the top. Then add lots of food coloring so you get a really bright color.


We used gel food coloring because it’s all we had on hand. It just required a little extra stirring. Any food coloring will do as long as you use the three primary colors.

Next you need to make six strips of paper towel or sturdy toilet tissue. We used three squares of tissue for each strip, folding them into thirds. This is another opportunity for your preschooler to get involved!

IMG_0965Insert each strip of absorbent paper into each glass or jar, making sure that the paper reaches down to the bottom of the colored water and the empty jar beside it. Each jar should eventually have two strips of paper in it, connecting to the jars on either side. Here you can see where we have started adding the paper. The paper should not arch up high between the jars. A nice, flat bridge is great.

As you continue to add strips of paper to each jar, the capillary action will begin, and the colored water will start to climb!



Capillary action – in action!

The colored water is using capillary action to move along the tiny gaps in the fiber of the paper. According to Science Kids in New Zealand, “It occurs due to the adhesive force between the water and the paper towel being stronger than the cohesive forces inside the water itself. This process can also be seen in plants where moisture travels from the roots to the rest of the plant.” The colored water is actually overcoming the force of gravity!

The colored water will continue to escape each glass until it finally begins to drip into the empty glasses. Given enough time, the water level in the empty glasses will rise until all of the water levels are equal. And what happens as the primary colors begin to mix together? You’ve got a Romping Rainbow!

IMG_0972 (Edited)




Now I should warn you, we started this late in the afternoon and had to leave it overnight to complete our rainbow. But it was super fun to see what happened as soon as we woke up the following day!

Next, we decided to add some practical application and art to our experiment. After removing the tissue paper, Bryn used the colored water to paint with! How fun!


Watercolor painting with the Romping Rainbow

This week I will be sharing videos from our experiment on Facebook and Instagram. Be sure to follow me so you don’t miss out! (There are buttons on my sidebar.) I upload videos and short blog posts there throughout the week and then write more in-depth posts for my blog that go up on Mondays. I hope you’ll come back and visit again soon.

And don’t forget, my Ivy Kids activity box giveaway for kids ages 3-8 is live until midnight, July 31, 2017. Check out my Ivy Kids subscription review and enter while you can!






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