LEARN: Walking Rainbow Experiment

Walking rainbow experiment setup with 7 jars, paper towels and watercolour paints

Learning Activity: Walking Rainbow STEM Experiment

Some experiments need fancy equipment. This one needs paper towels, a few jars of water, and a quiet afternoon.

The Walking Rainbow is one of those rare activities that genuinely surprises children — and adults. You set it up, walk away, and come back to find colour has moved. It feels like magic. The science behind it is just as fascinating.

It's also beautifully open-ended: there's predicting, observing, recording, and a little artwork waiting at the end. Perfect for curious minds from preschool through to primary school.

What your little learner will discover

That mixing primary colours creates something new — and a little unexpected
How scientists think: predict what will happen, watch carefully, then explain what you saw
That water can travel upwards — and why that matters in the natural world
The science behind it: capillary action — the same process that pulls water from a plant's roots all the way up to its leaves

Preparation

Gather the following before you begin:

Paper towels — the more absorbent the better, but any will work
7 small jars — we used the Mercurius Glass Jars, but any small jars work just as well
Watercolour paints or food colouring — we used Stockmar Aquarelle Watercolours, but any paints or food colouring work too.

Record Your Experiment

We've created free printable recording sheets — two versions to suit different ages:

Pre-writers: circle and draw responses
Early writers: write predictions and observations in their own words

Download your free recording sheets

Primary colours mixing to make secondary colours in walking rainbow science experiment

Stockmar Aquarelle Watercolours used in walking rainbow experiment for kids

Let's Experiment

Step 1. Tear off 3 paper towels, cut each in half, then fold each piece into a long thin strip.

Step 2. Line up 7 jars. Fill jars 1 and 7 with red watercolour, jar 3 with yellow, and jar 5 with blue. Leave jars 2, 4 and 6 empty.

Step 3. Ask your little learners to make their predictions — what do they think will happen? Then place a paper towel strip between each jar, just touching the bottom. Trim if needed.

Step 4. Now sit back and watch the magic. The first movement usually appears within 5–10 minutes, with full colour mixing taking 1–2 hours — a wonderful slow experiment to return to throughout the day.

Step 5. Encourage your learners to record what they observe. What's happening? Why are the colours changing? Why is the water moving up? Older children can work through the explain section together.

Step 6. Don't let those beautiful colours go to waste — paint with your Stockmar Aquarelle Watercolours, or pop the lids on your Mercurius paint jars and save your rainbow for another day.

Happy experimenting!

Get your free record sheets

Take It Further

Loved this experiment? The Walking Rainbow is a wonderful entry point into understanding plant biology, colour theory, and the scientific method.

Simple materials, big ideas. This kind of hands-on experimenting builds the foundations of scientific thinking — curiosity, observation, and the confidence to ask why. It also opens up beautiful conversations: about how plants drink, how colours are made, and how paying close attention to the world around us is a skill worth practising at any age.

For more hands-on STEM activities and the toys and materials that support them, explore our STEM Through Play collection →

Open-ended, screen-free, and genuinely fun — because the best learning rarely feels like learning at all.