demonstrations:color_swirling_milk

Color Swirling Milk

Materials: ★☆☆ Easy to get from supermarket or hardware store
Difficulty: ★☆☆ Can be easily done by most teenagers
Safety: ★☆☆ Minimal safety procedures required

Categories: Fluids and Surface Tension

Alternative titles: Magic Milk, Soap and Milk Surface Tension

Summary

Food coloring on milk stays mostly still until a drop of dish soap touches the surface; swirling patterns then race across the milk as soap disrupts surface tension.

Procedure

  1. Pour about 1–2 cm of milk into a shallow dish.
  2. Add small drops of different food colorings spaced apart on the milk’s surface.
  3. Dip a cotton swab into liquid dish soap so the tip is wet but not dripping.
  4. Touch the soapy tip lightly to the milk’s surface near a color drop and watch the colors shoot away and swirl.
  5. Move the swab to new spots (re-soap as needed) to create additional motion and patterns.

Milk Food Coloring And Dish Soap Experiment - Incredible Science:


Magic Milk Experiment Using Food Coloring, Dish Soap, and Milk (Chemistry) - BeardedScienceGuy:


📄 Color Swirling Milk Experiment - C.S. Mott Children's Hospital: https://www.mottchildren.org/posts/camp-little-victors/color-swirling-milk-experiment

📄🎞️ Milk magic - Science Museum Group: https://learning.sciencemuseumgroup.org.uk/resources/milk-magic/

Variations

  • Compare whole, 2%, and skim milk to see how fat content changes the motion.
  • Try different soaps (hand soap vs. dish soap) or dilute the soap with water to test strength effects.
  • Chill one dish of milk and warm another slightly to observe temperature effects on flow.

Safety Precautions

  • Do not drink the milk.
  • Use a shallow, stable dish on a flat surface to prevent tipping.

Questions to Consider

  • Why does the milk barely move until the soap touches the surface?
  • How does soap change surface tension, and what role do milk fats play?
  • Which milk (whole, 2%, skim) produced the strongest swirling, and why?
  • Why does the motion eventually stop even if color remains?
  • How would warming or cooling the milk change the patterns you see?