Grow a Rainbow Experiment

Want to grow your own rainbow? Try this simple science experiment! You only need paper towel, water and washable markers. Kids will love to see their rainbow “grow” in this easy activity!

You will love seeing the rainbow come together in this simple science experiment! You can even do different patterns and colors too.

Here is what you will need for this activity:  

  • Paper Towel
  • Washable Markers
  • Water
  • 2 Small Glasses

What is the Science Behind This Experiment?

This science experiment is a great example of chromatography. Chromatography is a way of separating out a mixture of chemicals. If you ever got a paper with ink wet you would have seen the ink move across the page in streaks.

Capillary action makes the marker dye move up the paper towel.  The water moves upward through the paper towel, lifting the washable dye molecules with it. Because the washable markers are water based, they disperse in water.

Set up a few different scenarios and hypotheses. For example, if you were to try this experiment without any dye, you would still see the water rising upwards towards the center of the paper towel.

If you were try this experiment with permanent markers it would not work. This is because the markers are not water based (they are alcohol based) so the dye in the marker does not travel with the water. You can also show that permanent markers will disperse with rubbing alcohol but not with water.

Tips: 

  • You need absorbent paper towel or napkin – we used the brand Bounty
  • You must use washable markers – make sure to check it’s washable as not all Crayola brands are washable
  • Do not place the end of the paper towel too deep into the water or the dye will dissolve into the water instead of traveling up the paper towel
  • The shorter the paper towel – the better it works as there is less for the marker dye to have to travel across
  • Add lots of marker to the ends.  You need lots of dye for it to travel upwards.

Growing Rainbow Experiment Instructions

1. Fold over a piece of paper towel (so you have 2 pieces on top of each other). Trim the length to be 7.5 inches (any longer and the rainbow may not connect fully).

2. Draw rectangles of the rainbow colors on each end.

You want to make sure to fill these colors in well so there is enough dye to travel across the paper towel.

TIP: Add lots of marker to the ends, you want a good amount of dye to travel up the paper towel.

3. Place 2 cups with water filled 3/4 full. You only want the bottom of the paper towel in so leave some space from the top of the cup.

Then place the paper towel into the cups, with one end in each cup.

4. The washable marker dye with slowly make it’s way up with the water to meet the other side in the center of the paper towel.

5. Leave the paper towel for 10-15 minutes and it will eventually connect the colors together.

We love how simple this science experiment is! Expand on the learning by testing with permanent markers or just water to see what happens in those scenarios.