Easy⏱ time15 min$ cost2
Colour-Changing Milk
A drop of soap sends food colouring swirling across milk in bursts of motion.
Start building ↓
Result first
The build
Step 01
Pour the milk
Cover a dish with a layer of milk.
Step 02
Add colours
Drop several colours in the centre.
Step 03
Touch with soap
Dip a soapy swab into the milk.
Step 04
Watch it swirl
Colours race outward in patterns.
Working Principle
Soap breaks the milk's surface tension and grabs onto its fats, and that sudden rush of moving molecules drags the colours along.
The science behind it
A closer look
The reaction between soap and fat keeps the surface in motion until the soap is evenly spread, so the swirling slows over time.
Take it further
Variables to test
- 1 Compare whole vs skim milk — which swirls more?
- 2 Try warm vs cold milk for speed.
More Chemistry
Chemistry
Lemon Battery Array
Wire lemons with zinc and copper electrodes in series to light a real LED from fruit.
Easy⏱25 min$6
Chemistry
Reaction Volcano
Baking soda and vinegar erupt on cue while you measure how the ratio changes the blast.
Easy⏱30 min$7
Chemistry
Elephant Toothpaste
A catalyst makes hydrogen peroxide erupt in a giant foam column in seconds.
Medium⏱20 min$8