Walking Rainbow Experiment - You Shall Not Pass! Edition

You know when you attempt an experiment and it completely and utterly fails? Yeah, so that happened. But we were able to turn it into a fantastic study into scientific principles and the scientific method. In fact, it ended up being a much better lesson than if we hadn’t messed up. Yeah for failures! Wonder which experiment? It was the very simple walking rainbow challenge. And I completely screwed it up! Let me tell you more.

Rainbow Walking Water Science Experiment

What you will discover in this article!

The Walking Rainbow science experiment should have been easy, but due to a mistake we discovered a fascinating capillary action and natural balance project.

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We are at the end of our school year. It’s been a HARD year! So I thought we would do a fun and easy science experiment that would bring a little color to our lessons and get the kids engaged and doing some fun activities. I chose the Walking Rainbow challenge.

Easy peasy lemon squeezy! All we had to do was make water walk. Seems easy enough!

Experiment Fail

Except I didn’t really do any research or read up on the activity. I was winging it. This was PRESCHOOL level stuff. So easy! I wanted a no prep STEM activity, but forgot that no prep doesn’t mean no research!

I grabbed 6 mason jars, Set them up in a little circle. Added equal amounts of water to each one. Then the kids added red to the first one, left one empty cup, yellow, skip, blue, skip. We talked about what colours were in the rainbow and learned the ROY G BIV (Red, Orange, Yellow, Green, Blue, Indigo, Violet) trick for remembering them.

Then we carefully folded up our paper towels, and placed them in our jars and waited for the magic to happen!

A few days later our colours had hit a major roadblock. Literally! The colored water defied gravity and climbed up the paper towels and then stopped. We waited a whole week and other than the colours getting more intense on the one side, nothing else happened.

A few days later our colours had hit a major roadblock. Literally, they climbed up and stopped. We waited a whole week and other than the colours getting more intense on the one side, nothing else happened.

Research Time

It was as if Gandalf himself was standing there declaring:

You shall not pass!!

Never one to give up, we sat down and studied what was happening in our rainbow walking water science experiment.

We learned that the experiment was about capillary action and the water travelling through the paper towels. We assumed, wrongly, that the primary colors would mix in the fold of the paper towel strips, and therefore mix in the various jars giving us our rainbow colors.

Instead the clear water and the coloured waters came up against each other and stopped. They didn’t mix in the paper towels.

Interesting… very interesting…

It was time to do some research and we learned that the middle jars where we didn’t add any food colouring, actually needed to be left empty. The mixing of the colors happens when the waters mix in the jars, not in the paper towels.

D’Oh!

Rainbow Water Experiment Directions

We set up again. This time we did:

Cup #1 – a few drops of red food coloring and water
Cup #2 – empty cup
Cup #3 – a few drops of yellow food coloring and water
Cup #4 – empty cup
Cup #5 – a few drops of blue food coloring and water
Cup #6 – finally another empty cup.

Then we folded our paper towel, making sure it wasn’t too long, but just long enough to touch the bottom of each jar.

We watched and waited. In a couple of days we had our rainbow colours! Red, orange, yellow, green, blue and purple!

Walking Rainbow Science Beautiful Color Science

Nature’s Balance

But we were curious, so we waited a whole week to see what would happen. We were rewarded with a wonderful demonstration of how the whole system brought itself into balance.

I talk to the kids a lot about the delicate balances in nature and this experiment provided the perfect visual representation.

After a week the water levels in all the jars balanced and became even. Each jar had exactly the same amount of water.

Science Explanation

The Walking Rainbow Experiment explores a few basic scientific concepts.

Capillary Action

At a basic level, when you fold paper towels and place them between two jars and one is filled with liquid, they demonstrate capillary action. A paper towel is made from cellulose fibers which have gaps. The water is able to travel through the gaps in the fibers. The water is able to move upward, against gravity, because of the attractive forces between the water and the fibers which act like capillary tubes.

Capillary action is how plants pull water from the soil, through the plant’s roots, and up into their leaves, we explored this concept in our Pollution Experiment.

For your older students, you can explore more technical details such as how the intermolecular forces between the liquid and the paper towel creates surface tension. This surface tension reacts with the adhesive force between the liquid and paper towel. This causes the water to move up the paper towel and eventually into the next jar. Where it eventually fills the second jar with water.

Dig into surface tension with our Magic Milk Experiment.

Science of Colour Mixing

The science of colour mixing is also part of this experiment. As the paper towels pull water molecules they also pull the food colouring from the original red, blue, and yellow primary color jars, it deposits that coloured water into the adjacent jar. This results in a mixing of the two colours from the adjacent jars, which gives us the secondary colours: orange, green, and purple.

Walking Water Rainbow

I set out planning on just bringing a little colour to our homeschool room, but this activity provided so much more. The learning and understanding for my kids went beyond a simple experiment and demonstrated something I want them to truly understand.

First: Nature wants to be in balance. It will work hard to find that balance. We need to do our best not to mess with that balance.

Second: Always do your research!

Also? It really was a beautiful experiment. And those colours? Stunning!