Watching Colour Climb: The Paper Towel Experiment at Sonas Woodbridge

Reading time: 3 minutes

A row of cups. Some hold coloured water, some are empty. A strip of paper towel folded between each pair. Then everybody waits.

What happens next is the reason this experiment has been a favourite in our STEAM Studio at Sonas Woodbridge. The coloured water starts to climb the paper towel, travels up and over, and runs down into the empty cup next door. Where two colours meet, a third colour appears that nobody put there.

The children were genuinely absorbed by it, watching the colour move between the cups and noticing the new colours being made along the way.

Why the water climbs

Paper towel looks solid but it is really a mesh of tiny fibres with tiny gaps between them. Water is drawn into those gaps and pulled along, even upwards against gravity. It is the same reason a spill runs up a tea towel instead of sitting where you dropped it.

We do not use the word capillary action with three year olds. We ask what they think is happening, and then we watch to see whether they were right.

The part that surprises them

The new colour is the moment the room goes quiet. A cup of blue and a cup of yellow sit either side of an empty one, and over the next hour the empty cup slowly turns green without anyone touching it.

A child who has seen that happen understands something about mixing that no amount of being told would achieve. They watched it arrive.

What they are actually practising

Predicting and then checking. The children were asked what they expected before anything moved. Some were right, some were not, and both are useful. That gap between what you expected and what happened is where scientific thinking begins.

Patience. This experiment does not resolve in thirty seconds. Children came back to the table again and again across the morning to see how far the colour had travelled. Learning to wait for a result, and to keep caring about it while you wait, is a genuinely difficult skill at this age.

Describing what they see. Educators keep the conversation running: is it moving, how far now, what colour is that, what do you think will happen next. Vocabulary arrives attached to something the child is watching with their own eyes.

Try it at home

It costs almost nothing. Six cups, water, food colouring in red, yellow and blue, and a roll of paper towel. Fill every second cup, fold strips of towel between them, and leave it on the bench.

Then let your child check on it every so often through the afternoon. The waiting is a real part of it.

Come and see a normal morning

Sonas Woodbridge is at 29 Morrison Road, open Monday to Friday from 6:30am to 6pm, and rated Meeting the National Quality Standard by the national regulator.

Book a tour at Sonas Woodbridge or read about our programs and the learning studios each centre runs.