Making butter in a mason jar is very simple but it is a timely and arduous task. The butter will need to be agitated (churned) to separate the buttermilk from the butter. You can use many methods to agitate the butter including a traditional churn, a simple mason jar, or an electric mixer.
Butter is made from milk which is a liquid consisting of fat globules and water. The scientific observation of the process of butter making is to damage the fat globules so the fat separates and amasses into a solid.
1 pint heavy cream
Pinch Salt (optional)
The directions provided are for the Mason jar method. Change as necessary to suit your chosen agitation method.
Place the cream in your container and bring to room temperature. (Allow to sit for about two hours)
Begin vigorously shaking until you begin to see the cream beginning to solidify. After fifteen to thirty minutes, you should have chunks of butter that have separated from the buttermilk.
Place a strainer over a clean container and strain. The liquid in your container is fresh buttermilk the chunks remaining in the strainer are butter. Refrigerate the buttermilk for later use.
Keeping the butter in the strainer, wash with ice-cold water to remove any remaining buttermilk. Wash until the water runs clear.
Work or knead the butter to extract any remaining liquid.
If desired add salt.
Mcgee, Harold. On Food and Cooking: The Science and Lore of the Kitchen. Rev Upd ed. New York: Scribner, 2004. Print.
Wolke, Robert L.. What Einstein Told His Cook: Kitchen Science Explained. null. Reprint. New York: W. W. Norton, 2008. Print.