Walking rainbow experiment
Watch colours travel and blend across a paper towel to create a rainbow in this simple science experiment!
Create a colourful "walking rainbow" using just paper towels, markers, and cups of water.
By colouring the edges of a paper towel and placing each end into water, you can watch the colours slowly travel, spread, and meet in the middle. As the water moves through the tiny fibres of the paper towel, it carries the ink along with it, gradually completing the rainbow before your eyes.
This simple experiment introduces the science concept of capillary action in a playful and visual way. The slow transformation feels surprisingly calming to watch, making it just as fascinating for grownups as it is for children.
There is plenty of room for experimentation too. Try different marker colours, paper towel brands, or water levels and observe how the results change. Some markers move quickly while others barely spread at all, adding another layer of discovery.
This activity supports early science learning, observation skills, colour recognition, and patience.
Whether you treat it as a STEAM experiment or simply enjoy the magic of watching colours move, this activity turns everyday household items into something memorable!
Materials
Prep / make
Step 1:
Fill two cups with a small amount of water.
Step 2:
Cut out or fold a strip of paper towel so it can bridge between the cups.
Step 3:
Colour thick sections near each end of the paper towel using markers, leaving a small gap in between
Play
Step 1:
Place one end of the paper towel into the first cup of water, and place the other end into the second cup.
Step 2:
Watch as the water travels upward through the paper towel.
Step 3:
Observe the colours spreading and blending toward the middle.
Step 4:
Experiment with different colours or setups and compare the results.
Extend
Rainbow Challenge: Try creating a full rainbow across the towel.
Science Chat: Talk about how plants use capillary action to move water too.
Pattern Play: Experiment with stripes, dots, or shapes instead of solid colouring.
Reuse & recycle: Lay out your strips to dry and use them to make a craft, scrapbook art or for open-ended play (mini beach towels, anyone?)
