Super Fun Colorful Milk Demonstration
Step 1: Put whole milk in a saucer. (whole milk is important here; 2% or creamer would probably also work)
Step 3: Add a drop of dishwashing detergent. Dawn was recommended, but we use an eco-friendly one and that worked out fine.
Step 4: Watch what happens.
Step 5: See the crazy swirls as the colors dance.
Sometimes they make fun patterns.
Step 6: Explain what's happening. I found Steve Spangler's explanation very good. (In a nutshell, the soap's hydrophobic ends are racing around trying to attach to the fat molecules in the milk.)
You can add another drop to watch the reaction longer.
We had so much fun with this demonstration that it had an encore performance after dinner. And in writing up this blog, I found that it's possible to do with Elmer's glue, which then hardens and leaves a lasting impression of this fun reaction. Look out for future art projects!