How It Works: Cream Separator

Enlarge Image Image Gallery Vintage cream separators on display along with related collectibles: cream and milk cans, oil cans and racks used when cleaning separators, a particularly tedious chore.

There were a lot of things I looked at with wonder while growing up on a farm in Kansas. One of the most intriguing was the cream separator. Every morning and evening, my parents poured the produce from 20 cows through the separator, which instantly divided cream from milk. The cream flowed into cans destined for town; the milk went into buckets that were dumped into a hog trough.

By the time I was in high school, though, the cream business had disappeared, along with any use for the cream separator. From that point on, area farmers adapted to the market for whole milk or got out of the dairy business. It’s no surprise, then, that most people today have never seen a cream separator work, let alone know how it works. Simply put, the separator uses centrifugal force.

Putting gravity to work

In its raw form, milk contains a mixture of large and small butterfat particles held in suspension because they weigh less than the other parts of whole milk. It’s not unlike drops of oil mixed with water.

In both cases, lighter material rises to the top when the mixture is left standing. Consequently, when whole milk sits for some time, the heavier skim milk gradually settles to the bottom of the container, while the lighter butterfat rises to the top.

The earliest methods of cream separation involved gravity. In one early method, milk was poured into shallow pans (2 to 4 inches deep) known as setting pans. The pans were placed in a cool, clean room for 36 hours, allowing the cream to rise to the top. At that point, it was skimmed by hand with a tool called a cream skimmer.

This method made it difficult to handle large amounts of milk. As much as 30 percent of the cream was left behind. What’s more, if the milk wasn’t properly stored, the cream could easily sour.

According to early calculations, if a cow produced 300 pounds of butterfat a year, the shallow pan system left at least 30 pounds of production in the skim milk. At 50 cents a pound, that 30 pounds of butterfat had a value of $15. Consequently, a dairyman with a herd of 20 cows, whose average annual butterfat production was 300 pounds each, would suffer an annual loss of $300 — more than enough to pay for a “modern” cream separator.

Deep-setting separation

Later methods of cream separation involved the deep-setting method. Milk was placed in tall cans (often referred to as shotgun cans) placed in tanks of cold water. Measuring about 8 inches in diameter and 20 inches tall, the cans typically held about 4 gallons. The small diameter of an individual can allowed the water to cool the milk quickly, while its height put gravity to work, resulting in more efficient separation. Again, the cans sat for several hours before the cream was dipped off the top.