stem activity for kids
Grow a Rainbow Science Experiment
preschool-1st grade
Looking for a fun and simple science experiment for kids that feels like pure magic? The Grow a Rainbow Science Experiment is the perfect way to introduce little learners to the wonders of capillary action—all while creating a beautiful rainbow with just a few household supplies!
Using paper towels, washable markers, and water, kids will watch in amazement as the colors travel up the paper towel and blend together, forming a full rainbow right before their eyes.
This hands-on STEM activity is a fantastic way to explore color mixing, absorption, and the science of water movement—all in a way that’s engaging and easy to set up.
Whether you’re a teacher looking for a quick classroom science demo, a homeschool parent searching for an exciting STEM activity, or a caregiver wanting a rainy-day project, this experiment is sure to bring smiles (and a little science magic) to your day.
Ready to grow your own rainbow? Let’s get started!
teaches
Capillary action & absorption
Color mixing & chromatography
Scientific method
Patience & focus
Cause & effect
STEM & critical thinking
directions
How to do this
Grow a Rainbow Science Experiment
- Fold a Bounty paper towel in half
- Cut the paper towel to 7.5 inches
With washable markers, color rainbow stripes on each side of the paper towel
-
Pour water into two cups
Place each end of the paper towel into the cups of water
Watch as the rainbow climbs up each side!
Continue watching until the rainbow meets in the middle
This will take about 5 mins or so
What's the science behind the
Grow a Rainbow Science Experiment?
Capillary action is how water moves through materials like paper towels, plants, and even our own bodies. Paper towels are made of tiny fibers, and these fibers have small gaps between them. When you dip the ends of the paper towel into the water, the liquid starts to climb up the fibers, just like how a straw pulls up your drink!
But what about the colors? That’s where the washable markers come in! These markers are made with water-based ink, which means the colors can dissolve in water. As the water moves up the paper towel, it carries the ink along with it. The colors keep traveling until they meet in the middle, blending together to create a full rainbow!
This same process happens in nature, too. Plants use capillary action to pull water up from the soil, through their roots, and into their stems and leaves. It’s how flowers and trees stay hydrated—even without straws or cups!
Isn’t science amazing? Now that you know how it works, try experimenting with different colors or paper types to see what happens. What if you use permanent markers instead of washable ones? What if you use saltwater instead of regular water? There’s so much to explore!
