Activities / Experiment
Walking water rainbow
Colored water climbs up paper towels and mixes into a full rainbow, all by itself.
- Ages4+
- Time10 minutes to set up, 1 to 2 hours to watch
- A grown-up helps withPouring and food coloring
How to make it
- Stand the six cups in a circle so they touch.
- Fill every other cup about three quarters full with water. Leave the cups between them empty.
- Stir red into the first full cup, yellow into the second, blue into the third.
- Fold each paper towel into a long strip. Put one end in a full cup and the other end in the empty cup next to it, all the way around the circle.
- Check back every 20 minutes. The empty cups slowly fill with orange, green and purple.
Why it works
Paper towel is full of tiny gaps. Water sticks to the paper and pulls itself up through those gaps, even against gravity. This is called capillary action, and it is how plants pull water up from their roots.
Try next
- Guess the new colors before they appear.
- Try a thicker and a thinner paper towel. Which one is faster?
Safety note. Food coloring stains. Cover the table and wear an old shirt. A grown-up should be nearby for the whole activity.
Watch it
The video for this activity is on its way. It will be on our YouTube channel first.
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