Potions – Colorful Swirling Milk

This activity doesn’t connect with any specific potion in Harry Potter, but it is fun, colorful, and kind of seems like magic.

Here is what to do:

1. Gather supplies
   • Milk (higher fat content will work better – we used whole milk)
   • Plate or bowl
   • Food coloring
   • Dish soap
   • Cotton swab
2. Pour milk into a bowl or onto a plate
3. Drop food coloring over top of the milk
4. Put dish soap on the cotton swab and touch it to the surface of the milk. You can touch the cotton swab repeatedly in different spots and the colors will continue to spread and swirl.

What we are seeing with this potion is the interaction of the molecules in the soap with the fat molecules in the milk. Milk is mostly water, proteins, and fat. When the cotton swab with soap comes in contact with the milk, the molecules in the soap are attracted to and move towards the fat. This movement disrupts the milk and things start moving round, which swirls the food coloring around. Eventually all of the fat molecules get tied up with the soap molecules (in micelles). Until that happens, additional contact of the cotton swab with soap will cause more swirling. 

Watch here: