Science Experiment: DIY Rainbow Milk Art

diy rainbow milk art

My son never gets tired of this DIY rainbow milk art activity. The basic premise is to add whole milk to a pan (this is important; the fat in the milk is what makes this experiment work), then food colouring, then finally dish washing liquid. As you add the soap, the colours begin to dance and the milk transforms into a swirly tie-dyed pattern. 

Read on to see how to do this experiment with your kids, and to learn the science behind it.

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milk detergent food colouring pie tin


  • whole milk (NOT low fat or skim)
  • baking pan
  • food colouring kit
  • dish wshing liquid
  • 1 adorable child


kid pouring milk into pie tin

Step 1: Have your child help pour some milk into the pan (about 5 cm full).

squeezing milk into pie tin

Step 2: Squirt a little bit of each colour of food colouring into the middle. Notice that the food colouring sits virtually still on the milk.

rainbow food colouring in milk

Step 3: Now comes the fun part. Add one drop of dish washing liquid and watch the colours dance!

food colouring swirled in milk

squirting dish soap into rainbow milk

Step 4: Keep adding a few more drops in areas where colours are congregating. The fat particles in the milk will move away from the soap, taking colour with them.

food colouring milk swirl art

My kids are always totally entertained by watching the colours dance in the milk.

So, what’s happening here?

Milk is mostly made up of water, but it also contains fats and proteins. The fats in the milk are super sensitive to any changes in the liquid around it. Soap weakens the chemical bond that hold the protein and fat together. The soap causes the molecules of fat to move every which way, and the food colouring allows you to see this all in action. As the soap eventually gets mixed with the milk, the movement slows down—so if you add more soap, the action will likely start all over again.

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Images: Liz Stanley