The principle of a 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.
*SCAA Certified: A Specialty Coffee Association of America certification indicates the machine can heat water to a temperature between 195 and 205 degrees Fahrenheit and ensures that hot water will be in contact with coffee grounds for no less than four and no greater than eight minutes. It’s a solid confirmation of quality. But according to Joseph Rivera, a research coffee scientist at coffeechemistry.com, not every manufacturer chooses to submit their coffee makers for SCAA certification, and there are definitely great drip coffee makers out there without its stamp of approval. Six of the 10 coffee makers we tested are SCAA-certified — including all four of our top picks.