Want to grow a rainbow with just a paper towel and some markers? This grow a rainbow experiment is a super simple science activity for kids that’s as fun as it is colourful! With just a few household supplies, kids can watch as colours magically travel through the paper towel, blending together to form a beautiful rainbow.
This experiment is a great way to explore capillary action, the process that helps water move through plants. Plus, it’s the perfect hands-on way to introduce kids to STEM learning while creating a fun, colourful display. Whether you’re looking for a quick indoor activity, a classroom science experiment, or a creative way to teach about colours, this project is sure to impress!
Ready to grow your own rainbow? Let’s get started!
How to Grow a Rainbow
Materials:
- Paper towel
- Washable markers
- Water
Equipment:
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Baking sheet(optional)
Instructions:
Step 1: Find what you need
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Gather your supplies and materials.
Step 2: Draw rainbow colours on paper towel
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Cut a piece of paper towel to be 7 inches long and whatever width will fit in your glasses (we made ours 2-1/2 inches wide).You can generally get 2 rainbows from 1 piece of paper towel.
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Begin by drawing a red rectangle on one end of the paper towel with washable marker.Draw your rectangle about 1 inch long and just wide enough so that all the colours of the rainbow will fit equally on the end.
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Repeat on the opposite side, so the red section is across the paper towel from the first rectangle.
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Repeat, filling in the rest of the paper towel ends with rainbow colours.Go in order using red, orange, yellow, green, blue, and purple OR red, orange, yellow, green, blue, indigo, and violet — depending on what colours of marker you have.
Step 3: Insert the paper towel ends into water
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Fill 2 glasses of water between 1/2 and 3/4 full and set them down next to each other.
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Place one end of the paper towel in one cup and the opposite side in the other cup.
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Watch as the colour immediately begins to spread up the paper towel with the water.(You may also see some of the dye go into the water like little fireworks, depending on if the marker is still wet on the paper towel and how deeply the ends are dipped into the water.)
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Continue to observe the colours traveling up the paper towel to make the rainbow connect in the center.This process will take between 10 and 15 minutes.Your grow a rainbow experiment is complete! Now have fun discussing how the experiment works (read more about this below).
Helpful Tips:
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Don’t oversaturate the edges: Only dip the edges of the paper towel into the water, as too much water can wash out the colours.
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Use fresh water for each test: Change the water for each rainbow you want to “grow”, since reusing the water may mix the dyes and change the results.
How does the grow a rainbow experiment work?
The grow a rainbow experiment works by using capillary action, the same process that helps plants draw water from their roots to their leaves. When the edges of a paper towel are placed in water, the liquid travels up the fibers of the paper towel, carrying the ink from the washable markers along with it. As the colours spread, they create a beautiful rainbow effect!
Since washable markers are water-soluble, their pigments dissolve and move with the water. Within minutes, you’ll see your rainbow “grow” from both ends of the paper towel toward the center, creating a fun and colourful science experiment!
What markers are needed for the grow a rainbow experiment?
For the best results, you’ll need washable markers. These are designed to dissolve in water, allowing the colours to spread up the paper towel.
Permanent markers won’t work because they’re waterproof, meaning the colours won’t travel with the water. (However, if you want to experiment, permanent markers can spread using rubbing alcohol instead of water.)
Most importantly, use fresh markers with plenty of ink. The more dye you get onto the paper towel, the brighter and more vibrant your rainbow will be!
What type of paper towel works to grow a rainbow?
A thick, absorbent paper towel is key to making your rainbow grow properly. Brands like Bounty or Kirkland work well because they absorb a lot of water without falling apart.
If you use cheap dollar store paper towels, they may disintegrate before the colours can spread. Some thinner store-brand paper towels may also be too fragile to draw on without ripping.
Why isn’t my rainbow growing properly?
If your rainbow isn’t spreading as expected, a few things could be causing the issue:
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Your paper towel is too long: The colours won’t reach each other in the middle if your paper towel is too long. Try using a shorter piece or just wait a little longer. The final stage of colour transfer takes the longest!
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Not enough marker was used: You need to really saturate the ends of the paper towel with colour. If there isn’t enough ink, the colours won’t spread as well.
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The paper towel was dipped too far into the water: If too much of the paper towel is submerged, the ink may dissolve into the water instead of travelling up the paper towel. Make sure just the very bottom of the paper touches the water.
By making a few adjustments, you’ll be able to grow a vibrant, full rainbow in no time!
This simple experiment is a great way to explore how colours move and mix in unexpected ways. It’s always exciting to watch the rainbow slowly form, and the best part is that every attempt turns out a little different! Whether your rainbow spreads quickly or takes a little extra time, the process itself is just as fun as the result.
If you enjoyed this activity, try experimenting with different colour patterns, using shorter or longer paper towels, or even testing different types of water (warm vs. cold) to see how it affects the rainbow. There’s always something new to discover!
Here’s even more easy science experiment ideas:
