Coffee Vacuum Brewer

The principle of a coffee vacuum brewer was to heat water in a lower vessel until expansion forced the contents through a narrow tube into an upper vessel containing ground coffee. When the lower vessel was empty and sufficient brewing time had elapsed, the heat was removed and the resulting vacuum would draw the brewed coffee back through a strainer into the lower chamber, from which it could be decanted. The Bauhaus interpretation of this device can be seen in Gerhard Marcks’ Sintrax coffee maker of 1925.

An early variant technique, called a balance siphon, was to have the two chambers arranged side-by-side on a sort of scale-like device, with a counterweight attached opposite the initial (or heating) chamber. Once the near-boiling water was forced from the heating chamber into the brewing one, the counterweight was activated, causing a spring-loaded snuffer to come down over the flame, thus turning "off" the heat, and allowing the cooled water to return to the original chamber. In this way, a sort of primitive 'automatic' brewing method was achieved.

On August 27, 1930, Inez H. Pierce of Chicago, Illinois filed patent for the first vacuum coffee maker that truly automated the vacuum brewing process, while eliminating the need for a stove top burner or liquid fuels. An electrically-heated stove was incorporated into the design of the vacuum brewer. Water was heated in a recessed well, which reduced wait times and forced the hottest water into the reaction chamber. Once the process was complete, a thermostat using bi-metallic expansion principles shut off heat to the unit at the appropriate time. Pierce’s invention was the first truly "automatic" vacuum coffee brewer, and was later incorporated in the Farberware Coffee Robot. 

Pierce’s design was later improved by U.S. appliance engineers Ivar Jepson, Ludvig Koci, and Eric Bylund of Sunbeam in the late 1930s. They altered the heating chamber and eliminated the recessed well which was hard to clean. they also made several improvements to the filtering mechanism. Their improved design of plated metals, styled by industrial designer Alfonso Iannelli, became the famous Sunbeam Coffeemaster line of automated vacuum coffee makers (Models C-20, C-30, C40, and C-50). The Coffeemaster vacuum brewer was sold in large numbers in the United States during the years immediately following World War II. [source : Coffee Vacuum Brewer]