Vacuum coffee maker

Since their invention these devices have been used in many parts of the world. While vacuum coffee makers generally were excessively complex for everyday use, they were prized for producing a clear brew, and were quite popular until the middle of the twentieth century. Vacuum coffee makers remain popular in some parts of Asia, including Japan and Taiwan. Design and composition of the vacuum coffee maker varies. The chamber material is borosilicate glass, metal, or plastic, and the filter can be either a glass rod or a screen made of metal, cloth, paper, or nylon. The Napier Vacuum Machine by James Robert Napier, presented in 1840, was an early example of the vacuum brewing process. The Bauhaus interpretation of this device can be seen in Gerhard Marcks' coffee maker of 1925. Balance siphon An early variation of this principle is called a balance siphon or Belgian brewer. This implementation has the two chambers arranged side by side on a balance-like device, with a counterweight attached to the heated chamber. Once the vapor has forced the hot water out, the counterweight activates a spring-loaded snuffer which smothers the flame and allows the initial chamber to cool down thus lowering pressure (creating a vacuum) and causing the brewed coffee to seep in. Automated version In 2022, the Japanese Tiger Corporation released an automated coffee-maker based on the vacuum coffee maker principle, which was marketed as the Siphonysta. The Siphonysta's heating is electrical. The chambers are made of plastic ("resin"). ==Brewing principle==

A vacuum coffee maker operates as a siphon, where heating and cooling the lower vessel changes the vapor pressure of water in the lower, first pushing the water up into the upper vessel, where the coffee is brewed, then allowing the brewed coffee to be strained as it is drawn back down into the lower vessel. Specifically, by heating (A) the water in the sealed lower vessel (B), the combination of its vapor pressure (the pressure exerted by the vapor component of a liquid) and the pressure from heating the air will exceed the ambient standard atmospheric pressure, causing some of it to boil, turning into water vapor. Since the density of water vapor is approximately that of liquid water, the mixture of air and water vapor in the lower vessel quickly expands as more liquid is boiled to vapor, increasing the pressure in the lower vessel. Once the pressure in the lower vessel exceeds atmospheric pressure, the remaining water is pushed up through the siphon tube (C) into the upper vessel (D), where it remains, so long as the pressure difference between the upper and lower vessels is sufficient to support it, about . This pressure difference is maintained during brewing through the continuous heating of the lower vessel. Coffee grinds are added to the water in the upper chamber and coffee is brewed using the displaced water at slightly less than the boiling point, . When the coffee has finished steeping, the heat is removed and the pressure in the lower vessel decreases; when the combined force of gravity and atmospheric pressure overcomes the (decreased) pressure within the lower vessel, the brewed coffee is pulled into the lower vessel of the vacuum coffee maker, leaving the coffee grounds in the upper vessel. The iconic Moka pot coffee maker functions on the same principle but the water is forced up from the bottom chamber through the third middle chamber containing the coffee grounds to the top chamber which has an air gap to prevent the brewed coffee from returning downwards. (Additionally, because the water is forced up through packed grounds, the pressures are greater.) The prepared coffee is then poured off from the top. ==See also==