With this walking rainbow water experiment, you can see things happening right away. Watch as the water walks up from one cup to another, making a pretty rainbow seemingly on its own.
We used 5 cups but you could make your rainbow even longer by using 7 cups and lots of different colours.
Time: 2 hours
Age: Little kids to Tweens
Difficulty: Easy peasy
Skill: Science – learning about capillary action
You will need:
- Plastic cups or glass jars – 1 for each colour
- Food colouring – as many colours as you would like
- Kitchen roll
Step 1: Set out your cups
Place 5 cups or jars in a row – about 2 cms apart.
Fill the 1st, 3rd and 5th cup with water – about two thirds full.
Step 2: Add some food colouring
Add food colouring to the water in each of those cups.
Choose colours that will blend well together later on in the experiment.
We put blue food colouring in the first cup, red food colouring in the third and yellow in the fifth cup.
Step 3: Fold some kitchen roll
Cut a sheet of kitchen roll pin half and fold it in two.
You need to make four thin strips of kitchen roll like this.
Step 4: Set up your walking water rainbow
Place one strip of kitchen roll into your first cup. Make sure the bottom of the strip reaches into the red water.
Then place the other end of this strip of kitchen roll into the empty cup next in the row.
Place your next strip of kitchen roll at the other side of the empty cup and bend it so it goes into the third cup filled with red water.
Keep adding strips of kitchen roll until you join up all the cups in your row.
You can see from our photo that almost immediately the water starts to walk up the kitchen roll.
Step 5: Wait for the magic to happen
Now sit back and wait for the water to walk up and down the strips of kitchen roll.
After about half an hour you will begin to see that not only does it colour the strips but begins to drip coloured water into the empty cups!
After 2 hours, all cups are full of liquid.
The previously empty cups (numbers 2 and 4) become mixes of the two colours on either side of them:
Yellow and red make orange liquid – blue and red make purple liquid.
The cups are now a rainbow of colours and the kitchen roll is its own rainbow of colours too.