Grow A Rainbow Experiment Growing A Rainbow Stem Activity

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!

Helpful Tips:

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: 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!