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Polluted Runoff: Nonpoint Source Pollution

Darby Duck, the Aquatic Crusader - Exploding Colors

You can see how quickly detergent molecules start to arrange themselves by doing this experiment:


  • two colors of food coloring
  • a cereal-sized bowl of milk (skim milk works best)
  • a spoonful of detergent


  1. Pour a few drops of each color of food coloring into the milk. Don't stir!
  2. Slowly pour some detergent along the side of the bowl and watch the colors explode.

How It Works

At first, the food coloring rests on top of the milk. The detergent weakens the pull of surface tension in the water where it rains down the side of the bowl. There is still a pull from the molecules on the opposite side of the bowl, so no food coloring is drawn over there. You can try the same experiment using baby powder or pepper instead of food coloring.