Milk, food coloring and liquid soap are all you need for this beautiful activity that doubles as a lesson in surface tension. Milk (and all liquids) contain a property known as surface tension. Surface tension is caused by the cohesive forces of the liquid’s molecules. Soap, when applied to any liquid, will reduce the surface tension. If this is the case, what will happen when we add liquid soap to the milk with food coloring droplets?


  • a shallow container (a shallow bowl or tray will work)
  • milk (we used about 1 cup)
  • liquid dish soap
  • a small container for the dish soap
  • q-tips
  • liquid food coloring



    1. Pour 1 cup of milk into a pie-sized shallow container.


    3. Squeeze several drops of different colors of food coloring into the milk.

    5. Squeeze liquid dish soap into a small container and dip a q-tip into the liquid dish soap.


    7. Dip the q-tip with the liquid dish soap into the milk with food coloring and watch as the colors almost magically move around!

    Alternatively, you can squeeze drops of liquid dish soap into the milk or dump a small container of dish soap right into the milk and watch what happens!

Caroline Gravino, a PBS Parents resident crafter, is a designer of creative family projects, tinkering painter and mother of four children. She writes about project ideas for the whole family and how to encourage creativity in kids on the popular blog, Salsa Pie and shares videos on the PBS Parents YouTube

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  • C Young

    Dear PBS – please include with your science videos a basic explanation and a link to more info so that we can keep the momentum going! If I have to prep by researching from scratch, or stop midstream to go to the computer, I am deterred from doing the activity. My being able (easily) to pose or answer some beginning questions on the spot is a prerequisite to developing inquiring minds! thanks

  • Debbie Feistner

    Can you place a piece of paper on top of the swirls and will it attach to the page for art to take away?

  • Emerson Kingsbury Jr

    Debbie did you ever try the piece of paper? Thanks