The Rainbow Milk Experiment

Here is a fun and easy experiment you can try at home with very few ingredients! Make your milk come to life with this experiment your kids can do again and again!

You need:

  • Milk (whole milk works best)
  • A dish (a shallow pyrex dish works best)
  • Washing up liquid
  • Food dye (colours are up to you!)
  • Q-tips/cotton buds
Fun science rainbow milk experiment

Photo from Steve Spangler Science


  • Pour some milk into the dish, enough to cover the bottom of the dish.
  • Add a few drops of food dye to the milk (mix and match the colours!)
  • Dab the end of the cotton bud into the washing up liquid
  • Finally, dip the cotton bud into the milk and watch!

The science behind it :

Milk contains (amongst other things) fats and proteins. When the washing up liquid comes into contact with the milk it weakens the chemical bonds between the fats, proteins and the rest of the milk.

The soap then attaches to the fat in the milk and this causes the cool patterns that we see! The soap molecules are moving round trying to find fat molecules to attach to. We can see this happening because of the food colouring; the soap and fat molecules bump into the food dye molecules causing them to move around. It will stop when all of the soap is mixed with the milk.

Thanks to Steve Spangler Science for this experiment!