Pour milk into the dish, about one-half inch deep.
Let the milk warm up to room temperature.
Place drops of different food coloring in the milk. Do not stir.
Place one to three drops of dish soap in the milk.
Watch the colors swirl.
How It Works
The colors move as the soap spreads across the surface of the milk. Once soap covers the surface, the swirling will stop. (If you use water instead of whole milk, the colors will start and stop in an instant.)
In whole milk, fat is the secret ingredient that keeps the colors moving. As the soap spreads out, it sticks to tiny globules of fat. As the globules take up soap, they make room for more soap to spread out.
