Walking Water Rainbow

Water climbs kitchen paper between cups and mixes new colours on its own.

Ages 4+Prep 10 min · Activity 15 minNo messIndoorLearningEasy

By WonderCraft Kids Editorial Team, Editorial team · Updated 7 August 2026

Set up seven cups, three colours and some folded kitchen paper, then walk away. Half an hour later the water has climbed uphill and made orange, green and purple by itself. Children come back to check on it repeatedly, which is exactly the point.

What you need

7 clear cups or glasses
Kitchen paper
Red, yellow and blue food colouring
Water
A tray to keep it contained

Step by step

1
Line the cups up in a row on the tray.
2
Fill cups 1, 3, 5 and 7 about three-quarters full; leave 2, 4 and 6 empty.
3
Colour cup 1 and 7 red, cup 3 yellow, cup 5 blue.
4
Fold kitchen paper into strips and bridge each pair of neighbouring cups.
5
Predict out loud what will happen, then set a fifteen-minute timer.
6
Come back and check. Full effect takes about an hour.

What kids learn

Capillary action

Water climbs the tiny gaps between paper fibres — the same mechanism that carries water up a plant stem.

Colour theory

Secondary colours appearing in the empty cups proves the primary-colour rule without a lecture.

Delayed observation

Returning to check a slow experiment is a different skill from an instant result, and a valuable one.

Make it easier

Use three cups and two colours so the first new colour appears in under ten minutes.

Make it more challenging

Draw a prediction chart before starting, then measure water levels every ten minutes.

Safety and supervision

Use plastic cups with younger children.
Food colouring stains worktops and clothes — keep the tray under it.
Remind them the coloured water is not a drink.

Adult supervision is required for every activity on this site. Read our full child safety guidelines.

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