How Vacuum Coffee Makers Work

History

Vacuum coffee makers (sometimes called siphon coffee makers) originated in Germany in the 1830s. These coffee makers were an innovation that dealt with a growing belief at the time that it was inappropriate to engage in boiling coffee beans or grounds in water. The concept was popular, and patents for variations on the vacuum design were issued across Europe. The double globe design that is common today among vacuum coffee makers can be attributed to Madame Vassieux of Lyons, who created the design in approximately 1841. Vacuum coffee makers did not reach the U.S. until around 1900. During the first half of the 20th century, vacuum coffee makers were quite popular; however, beginning in the 1950s, they were supplanted by automatic percolators and drip-style coffee makers. But since the late 1990s, there has been a resurgence of interest in vacuum-style coffee makers. An article by Brian Harris, The Historical Development of Vacuum Coffee Pots, offers an in-depth exploration of the development and history of vacuum coffee makers.

The Coffee Pot

Vacuum coffee makers are fundamentally different in nature than the more common drip coffee makers. Vacuum coffee makers do not employ carafes in the process of coffee-making. There are six major components to a vacuum coffee maker. First, there are two glass globes. One globe sits on the bottom. The other, which usually has a siphon tube attached, is set into the bottom globe and has an open top. There is a filter which can be made of a variety of materials including paper, glass, cloth and metal. Also, there's a stand to hold the assembled parts, and a gasket for the top of the upper globe to help create a seal between the top and bottom globes. Last is the heat source. Heat sources for vacuum coffee makers vary and can include alcohol and butane-based burners. Some models are designed to be used with the heating element of an electric stove.

Brewing

Vacuum coffee makers work through the use of a vacuum and the pressure created by expanding gas. When assembled, there is water in the bottom globe, and the siphon tube is in the water. The filter is on top of the siphon tube and grounds sit on top of the filter. The rubber gasket in the top of the upper globe creates a closed system in which there is a finite amount of space. As heat is applied to the bottom globe, a portion of the water is converted to vapor. Gases (in case high school chemistry is a distant memory) take up more room than a liquid. Since the coffee maker is a closed system, as the vapor expands, it pushes the water up through the siphon tube. As long as heat is applied to the bottom globe, the gas will remain in an expanded state and keep the water in the upper globe, brewing coffee. When the heat is later removed, the gases condense, the pressure is removed, and the coffee sinks back down the siphon tube, ready to be enjoyed.