How It Works: Cream Separator

Over the years, de Laval enhanced his original design. For example, his original separating bowl was a hollow cylinder containing wings to keep the milk rotating with the bowl. However, in 1890, his company developed the “Alpha disc” bowl, in which a number of conical steel discs were placed within the bowl, one above the other, spaced slightly apart. Fed into the center of the bowl as before, skim milk was separated from cream with less difficulty than in the hollow bowl, where the milk and cream were allowed to form a solid mass.

As centrifugal force was applied by a unit spinning at 6,000 to 8,000 rpm, the cream was delivered near the bottom of the bowl and gradually passed upward from the inner ends of the discs nearest the cream outlet. Skim milk was similarly passed upward during centrifugal motion, but because of its density, it passed outward through the spaces between the discs in thin sheets and was forced to the outer ends of the discs. In this cavity the skim milk passed toward an outlet through which it drained into a separate bucket or milk can. Unprocessed milk, meanwhile, was fed into the separator at a constant stream from a vat positioned above the bowl.

Progress through technology

From the start, the continuous flow separator offered farmers a huge advantage. In contrast to gravity flow systems, a well-adjusted centrifugal cream separator left less than one percent of the cream behind in the skim milk. Centrifugal force also produced a filtering effect that removed most of the foreign matter in the cream. 

Most important, though, farmers could milk more cows and increase their profits, since greater quantities of cream could be separated in less time. Within a matter of months, cream separators were being imported to the U.S. — primarily from Sweden — and farmers began to expand their herds.

Cream separators made their first appearance in the Sears, Roebuck & Co. catalog of 1896, while Montgomery Ward & Co. listed them as early as 1894. Sears sold the Young America cream separator, rated at 300 pounds of milk per hour, for $97, while Montgomery Ward offered the Safety Hand separator (with the same rating) for $125.

As noted on the Dairy Antique Site, cream separator manufacturers flourished in the early 1900s and prices dropped significantly. By 1902, Sears advertised its own Sears cream separator in 250-, 350- and 500-pound/hour sizes. The 350-pound/hour machine was priced at $63.75 (about $1,677 today). That was the start of the Sears Economy cream separator line. Cream separators continued to appear in Sears and Wards catalogs into the mid-1950s.