Here’s a fun experiment for a chilly, cloudy day during the North Carolina Science Festival. Watch as Summit School student Marin McCauley creates a kaleidoscope of colors in milk during this Kaleideum At Home video.
What’s the simple explanation for the complicated science behind this experiment?
Water has surface tension — a stretch, membrane-like surface. If you add soap to a water drop, it flattens, reducing the tension of the surface. Milk is mostly water, which means it also has surface tension. When the soap touches the surface of the milk, you reduce the tension. Since the tension at the spot being touched is weaker compared to the rest of the bowl, the water molecules elsewhere in the bowl pull water molecules away from the soapy spot. The food coloring reveals the currents in the milk.