Looking for cool science experiments for kids? Check out this rainbow walking water experiment that your kids will love!
This easy and fun science water experiment for kids is a great way to teach them about the properties of water and color through a hands on experience.
In this colourful rainbow water experiment, you’ll get to make new colours appear as if by magic. See the water walk and travel from one container to the next. It’s not magic though of course, just some cool science!
This easy science experiment is great for helping kids to understand about the properties of water and absorption. It also shows how primary colors can be mixed to create secondary colors.
Check out the video above to see how to create a paper towel rainbow.
If you prefer to read step-by-step instructions, you can find them below. You’ll also find a list of materials needed, a kid-friendly science explanation and a list of questions to help get your kids thinking.
Walking water science experiment materials
One of the best things about this rainbow science experiment is it can be done with just a few basic materials. You most likely have them already lying about at home.
If you don’t have any food dye or food coloring available, we highly recommend stocking up on some in as many colours as possible. Adding colour makes almost any STEM activity more exciting!
To do this simple rainbow science experiment at home, you’ll need a few simple supplies:
- Paper towel
- 5 small and shallow containers
- Food colouring (Primary colors like red food coloring, yellow food coloring & blue food coloring)
- Tap water
Some people have success with coffee filters instead of paper towels. We tried this and it didn’t really work for us. They didn’t absorb enough of the water and food colouring.
However, it may depend on the kind of filter you use. Feel free to give it a go if you don’t have any excess paper towel at home.
How to make a rainbow paper towel experiment
This walking water science experiment is super easy to do and it can be done in just a few steps.
Step 1. Put your containers or all the jars next to each other in a straight line. You want about a 2cm gap between each one. Pour water on them.
You can also use an empty glass or and empty cup as container for the walking rainbow experiment.
Step 2. Add a generous amount of food colouring to three of the containers. You need to use quite a lot. If you only use a few drops, there won’t be enough dye for the rainbow to fully appear.
Starting from the left, the first container should have red food coloring added. The third should have drops of yellow food coloring added and the fifth should have drops of blue food coloring added.You can use the same amount of food coloring for each container
Don’t add any food coloring to the second and fourth containers.
Step 3. Take a rolled paper towel strip and fold it into a half sheet or until it becomes a thick strip. You will need 4 sheets like this.
Step 4. Put the end of one of the strips in the first container on the left. Then another paper towel at the other end of the strip in the second container.
Step 5. Repeat all along the line of containers, so that all of them have two strip ends in them. Make sure both ends of each strip are underwater until the last paper towel.
Step 6. Now wait for the colours to start ‘walking’! You will see the colour start to move quite quickly. The paper towels will become full of water pretty much straight away.
You’ll need to wait a few hours to see colors mix and up to a couple of days for the experiment to fully become a rainbow walking water.
Note that more absorbent paper towels work better for this experiment. If you’re using a less absorbent paper towel, you may need to leave it for a few minutes longer to see the colours fully travel.
The colour in each container will make its way up the strips and into the next container. This will add colour to the containers with only water in. Having an empty jar or empty cups will not make this experiment work.
You’ll then see the colors mix and form new ones as water travel upwards and move from one container to another.
You should see a secondary color like green appearing between blue and yellow cup. Orange should appear between yellow and red. This is how secondary colors are formed by mixing the colors.
Mixing colors like this is always so satisfying to watch!
Questions to ask your kids about the walking water experiment
We’ve put together a few questions you can ask your kids to get them thinking about the walking water rainbow experiment.
Encourage your kids to to share their thoughts with each other. You can give your opinion too!
- Why does the colour move through the paper bridges?
- Does anything else travel with the food colouring?
- Why do you get orange and green water in the second and fourth containers?
- What is special about red, yellow and blue?
- What colours can you make by mixing other colours together?
- How do you make pink, grey, purple and brown?
- How long did it take for your rainbow to appear?
- What could you do to get brighter-coloured green and orange water?
A simple explanation of this walking water science experiment
This simple science water experiment works because of a a scientific method process called capillary action. Capillary action happens when a liquid travels up through a solid material which is hollow or has lots of tiny holes in it.
And because the paper towel fibers are porous, water can flow through them. The gaps in the paper towel serve as capillary tubes, drawing the water upwards. This works similarly to how water climbs from a plant’s roots going to the leaves at the top of the plant.
A liquid like water is actually quite sticky. Water molecules stick because of the attractive forces which make them stick to each other (‘cohesion’ or cohesive force). They also like to cling to the surfaces of other objects (called ‘adhesion’ or adhesive force).
A paper towel has lots of tiny holes inside. When you dip it in water, food dye molecules fill the tiny holes inside the paper towel. However, the water molecules still also want to stick to each other. This experiment appears to defy gravity as the colored water travels up the towel bringing other food dye molecules with them.
The water also takes the food colouring with it. This is why the colour moves across the bridges and into the containers with clear water in.
If you like science experiments like the walking water science experiment, we think your kids will love this colour-changing walking water activity.
In this fun cabbage Ph indicator activity, your kids can make ‘magical’ potions. Just by adding common household products, they’ll be able to make their potions instantly change colour!