What you need
- Two paper towels
- Water
- Food colouring- ideally two different colours
- Three Cups
Fold the two paper towels into two tubes roughly 20cm long.
Fill two cups with water and add food dye to each, ideally of different colours. To get the best effect, use undiluted food colouring or at least very strong!
Place an empty cup between the two full cups. Place one end of a paper tube into one cup filled with coloured water and the other end into the centre empty cup. Repeat this step with the other cup of coloured water and paper towel, so that the cups and paper towels alternate as follows: cup, towel, cup, towel, cup.
Wait for several hours. If you would like to see the process more clearly set up a time-lapse camera to watch over your experiment!
Go further – try to arrange the colours and cups to make a rainbow!
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What is happening?
Water has a strange ability called ‘capillary action’ where, due to its stickiness (surface tension, adhesion, and cohesion), it can travel through materials without the assistance of other forces. Because of this, the dyed water travels through the paper towel and into the empty glass. If you had used two different dyes you should have seen the colours mix in the middle glass.
Variables to test
- Does it make a difference with hot vs. cold water?
- Try different food colours… what is the result?
- Try tissue paper, vs. paper towels vs. printing paper
Working with Water
Years K to 2
Maximum 30 students
School workshop (NSW & VIC)
60 or 90 minutes
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Years 3 to 6
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This experiment is so fun!
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