What you need:
A glass jar with a tight-fitting lid, a marble, liquid heavy cream, a friend for help
What to do:
1. Fill the jar halfway with the cream.
2. Clean the marble well. Pat it dry and drop it into the cream-filled jar.
3. Seal the jar tightly and begin to shake.
4. Keep rolling and shaking the jar for about 30 minutes. You and your friend can take turns doing this. You can even open the jar intermittently and check what’s happening inside.
What happens:
The liquid cream gradually thickens and solidifies into butter that settles at the bottom of the jar, leaving a milky liquid floating on top. Separate the liquid (and the marble) and store the butter in the refrigerator.
Why?
Heavy cream liquid has a lot of fat in it. These fat molecules are usually inside globules i.e. stretchy membrane-like balls (somewhat similar to a teeny-tiny balloon filled with water). When shaken about, the globules smash against one another and burst. This causes the fat molecules inside them to flow out and start sticking together. So, these molecules separate from the liquid and clump together to make butter.
Picture Credit : Google
