Do you have a kid who loves rainbows? or maybe you love rainbows and would love to grow one yourself.  Try this simple Growing Rainbow Shapes activity and amaze your little learners.

This science and art project is pretty easy to do and with just a few ingredients you can grow your very own rainbows shapes. It is a great exploration of capillary action and an extension of shapes and geometry. You can try different patterns and colours and watch the colours mix and grow.  

So without further ado …

Let’s get growing!

How to Grow Rainbow Shapes

What you need:

• Paper towel
• Washable markers
• Small containers /cups
• Water

How to:

This activity is pretty simple to do and with just a few steps you can watch the magic happen in front of your eyes. For a quick demonstration and instructions, watch the video or follow the steps below.

Step 1: Cut strips of paper towel. Tip: Use absorbent tissue or paper towel and keep the strips short. The shorter the ink has to travel the more vibrant the results will be. 

Step 2: On both ends of the paper towel strips, draw rainbow colours in rectangular blocks. Tip: draw over the rainbows a couple of times. You want to add a lot of dye to get a vibrant rainbow.

Step 3: Form different shapes using your containers (without water) and paper towel strips. This will require some tweaking and trial and error. For example, to create a triangle you need 3 containers which will be where the points of the triangle should be. The strips will make the edges of the shape. Tip: only a small portion of your paper towel strips should be in the container / come in contact with the water. 

Step 4: Fill the containers with water. You may have to gently push the ends of the paper towel so that it comes into contact with water. Watch the rainbow shapes grow. Tip: When immersing the paper towel end in the water, make sure not to submerge it too deeply; otherwise, the dye will dissolve into the water instead of travelling up the paper towel.

The STEAM behind the fun:

This math, art and science experiment is a great example of chromatography. Chromatography is a technique used by chemists to separate a mixture of chemicals. In laboratories, they use a special machine to do chromatography. But the fun thing about science is, you can do some of the experiments at home without machines, just like this one. In this growing rainbows experiment, we are separating the colours of the ink which is a mixture of chemicals. The ink is separated by a process called capillary action. 

When you add water to the paper towel, the water spreads through the paper towel through capillary action. Capillary action is the movement of fluid through small spaces. The paper towel is made of very small veins or tubes that we can’t see. As the water spreads, it carries with it the colour molecules. You will notice some colour molecules took a little longer than others to spread. This means the ink is made up of heavier molecules. This is a similar procedure to chromatography. 

Explore further:

• Try different shapes
• Try different types of markers. Can you grow a rainbow with all types of markers?
• Try different types of paper towels, tissues, coffee filter and paper.  Which material is the best?
• Use only primary colours, red, yellow, and blue. Experiment to create new colours. 

We love simple experiments that you can do at home and learning complex concepts. Explore and expand on the learning by making a hypothesis and testing different markers and papers.  We hope you try out this simple activity and watch the magic of science help you grow Rainbow Shapes. Happy experimenting!