Instructions: How does sea foam form?

Materials

  • Milk (different kinds of milk produce different foam)
  • A clear, microwave-safe glass jar, ideally with a leakproof lid
  • A microwave or appliance to warm milk
  • Optional: milk steamer, milk frother, blender, or handheld mixer; ruler; timer or stopwatch; water; flavoring such as cocoa.
A looping GIF showing a close-up view of hot chocolate in a mason jar being mixed by a handheld milk frother. As the milk froths, pale foam builds up on top of the hot chocolate.

Video: How does foam form?

Watch as Audrey Maran with NOAA's Office of Education demonstrates this activity at home and explains how seafoam actually forms in a very similar way to the milk foam for your favorite latte!

Directions

  1. Warm up your milk in the glass jar, but not too much! You should be able to hold your hand to the jar comfortably. 
  2. Add air to the warm milk. You can use a milk steamer or milk frother, a blender, handheld mixer, or simply put a leakproof lid on the jar and shake up the milk by hand. 
  3. Make and record observations about the height of the foam, how long the bubbles last, and the size of the bubbles. 
  4. Try an experiment! Formulate a question that can be answered through further investigation. Here are some ideas to expand on what you’ve already done. Be creative with your variables, but remember to choose just one variable to test at a time.
    1. Use a ruler to measure foam height: Shake the milk. Measure the foam height, or distance from the surface of the milk to the top of the foam with a ruler. Then add flavoring such as cocoa. Shake the flavored milk. Measure the foam height again. How did the added ingredient affect foam height? Why?
    2. Use a timer to measure foam longevity: Choose two warm liquids such as soy milk and whole cow’s milk. Which milk do you think will create the longest lasting foam? Why? Warm both milks similarly. Shake the milk. Then time how long it takes for the foam to disappear. Which foam lasted longer? Why?
    3. Use a thermometer to measure milk temperature: Heat jars of milk to different temperatures. Shake the milk. Did the temperature affect the size of individual foam bubbles? Why?
    4. Use water as a control: Heat it to the same temperature as the milk, shake, and compare.
A looping GIF showing a close-up view of hot chocolate in a mason jar being mixed by a handheld milk frother. As the milk froths, pale foam builds up on top of the hot chocolate.
A looping GIF showing a close-up view of hot chocolate in a mason jar being mixed by a handheld milk frother. As the milk froths, pale foam builds up on top of the hot chocolate. (Image credit: Audrey Maran/NOAA)
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Two students stand over a mason jar of foamy milk. One student is bent over holding a cell phone to take pictures of the foam.
Students using milk to perform an experiment on sea foam formation. (Image credit: Courtesy Denise Harrington)