Milk and dish soap colour explosion
Recommended age: 6+. Adult supervision required! On a plate of milk, drops of food colouring burst into swirling colours on their own the moment dish soap touches them — the most spectacular demonstration of surface tension.
Chemicals
- 200 ml milk (2.8% fat or richer — the fattier, the more spectacular) — 2.8% fat or richer — the fattier, the more spectacular
- pc food colouring (3-4 colours) (a few drops of each colour) — a few drops of each colour
- 1 tsp dish soap (poured into a small dish) — poured into a small dish
Procedure
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Put on your goggles and work under adult supervision! The milk on the plate cannot be drunk after the experiment because dish soap gets into it — pour it away at the end and wash your hands.
Safety! -
Pour the milk into the shallow plate so it just covers the bottom, and let it settle for half a minute.
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Drip a few drops of 3-4 food colours onto the milk surface, around the middle of the plate. Do not stir!
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Predict: what will happen when dish soap touches the milk?
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Dip the tip of the cotton bud into the dish of soap.
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Touch the bud to the middle of one colour drop and hold it still — the colours practically explode and start to swirl!
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Touch other spots on the surface too and watch how long the dance lasts. When it slows down, do not be disappointed — that is part of the result.
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Repeat with low-fat milk or plain water — how much weaker is the effect? Fat is the key to the difference.
Technique -
At the end, pour the milk down the drain, wash up and wash your hands.
Apparatus
- 1× shallow plate — világos színű
- 2× cotton bud
- 1× small dish for the soap
Frequently asked questions
- Why does it work?
- Surface tension holds the surface of the milk together like an elastic film. The soap molecules tear this film at one point, then race around chasing the tiny fat droplets in the milk — the food colouring simply makes this otherwise invisible swirling visible.
- Why does the colour dance stop?
- Once the soap has spread everywhere, there is no longer any difference in surface tension to move the milk. With fresh milk and a clean plate you can restart the show any time.
- Does it work with water?
- Much more weakly, because water has no fat for the soap to chase. That is exactly what makes it a good comparison experiment: try it with whole milk, water and low-fat milk, and you see the role of fat immediately.
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Every version of this image is kept. Nothing here was photographed in a lab — the illustrations are generated on ATAILA hardware, and when the models or the prompt improve we regenerate and keep the old one so the difference is visible.