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ANSWER: What you have is what’s commonly called a “rocking churn.” It seems women used to hook the churn to a rocker using a hook and a length of rope and as they rocked, they pulled the churn from side to side, agitating the cream inside.
To better understand how this type of churn works, it’s important to know how the churning process works. Women used a variety of churns to turn cream into butter. The most common type of churn is the vertical churn into which a person inserted a pole inserted through the lid.
The agitation of the cream, caused by the mechanical motion of the device, disrupts the milk fat. This movement breaks down the membranes that surround the fats in the cream, forming clumps known as butter grains. These butter grains, during the process of churning, fuse with each other and form larger fat globules. The mechanical action introduces air bubbles into these fat globules. The butter grains become more dense as fat globules attach to them while action forces the air out of the mixture. This process creates buttermilk. With constant churning, the fat globules eventually form solid butter and separate from the buttermilk. The butter maker then drains off the buttermilk and squeezes the butter to eliminate excess liquid, forming it into a solid mass.
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Before commercial dairies began producing butter, every home had tools to make its own. Butter churns came in a variety of styles. The most common is a container, made of stoneware in the mid-19th century and later of wood, where the person making the butter creates it by moving a pole, inserted into the lid, in a vertical motion. This type of churn is also known as an “up-and-down”’ churn, plunger churn, plumping churn, or knocker churn. The staff used in the churn is called a dash, dasher-staff, churn-staff, churning-stick, or plunger.
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Finally, there the rocking chair butter churn, invented by Alfred Clark. This device, invented by Alfred Clark, consisted of a barrel attached to a rocking chair. While the rocking chair moved, the barrel moved and churned the milk within into butter. Today, a rocking butter churn in good condition sells for over $500.