This experiment is close to my heart as it is one of the first ones I did with the boys. This is the experiment that my preschooler tells his friends that they can ‘come to our house and see an amazing experiment’. And it’s the experiment that got my preschooler asking to do an experiment every day. So, it comes highly recommended – and it’s very easy to do!
Take 7 glasses, the same size/shape if possible (or as close as you can) and set them in a line so the glasses are touching. Fill glasses 1,3,5 and 7 with equal volumes of water (close to the top). Then put red food colouring in glasses 1 and 7, yellow in glass 3 and blue in glass 5. Finally, take 6 pieces of kitchen towel and fold them lengthways into strips. Then place then over the rim between each glass, so that the kitchen towel is in the water of the filled glasses. And wait…
After 24 hours or so, you will start seeing a beautiful rainbow as the water redistributes and the colours start mixing. Leave it another 24 hours for the best rainbow.
The science behind it…
The water moves along the kitchen towel and into the glass next to it because of a process called capillary action – the adhesive forces between the water and the kitchen towel are stronger than the cohesive forces within the water. The rainbow comes from the colours mixing!
This was so cool! Thank you for sharing!