Coffee makers are cooking appliances used to brew coffee without having to boil water in a separate container. While there are many different types of coffeemaker using a number of different brewing principles, in the most common devices, coffee grounds are placed in a paper or metal filter inside a funnel, which is set over a glass or ceramic coffee pot. Cold water is poured into a separate chamber, which is then heated up to the boiling point, and directed into the funnel. This is also called automatic drip-brew.
For hundreds of years, making a cup of coffee was a deceptively simple process. Roasted and ground coffee beans were placed in a pot or pan, to which hot water was added, followed by attachment of a lid to commence the infusion process. Throughout the 19th and even the early 20th centuries, it was considered adequate to add ground coffee to hot water in a pot or pan, boil it until it smelled right, and pour the brew into a cup.
The first modern method for making coffee-drip brewing-is more than 125 years old, and its design had changed little. The "Biggin", originating in France ca. 1800, was a two-level pot holding coffee in an upper compartment into which water was poured, to drain through holes in the bottom of the compartment into the coffee pot below. Around the same time, a French inventor developed the "pumping percolator", in which boiling water in a bottom chamber forces itself up a tube and then trickles (percolates) through the ground coffee back into the bottom chamber.
Other coffee brewing devices became popular throughout the nineteenth century, including various machines using the vacuum principle. The Napier Vacuum Machine, invented in 1840, was an early example of this type. While generally excessively complex for everyday use, vacuum devices were prized for producing a clear brew, and were actually quite popular up until the middle of the twentieth century.
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.
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 invented 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 in the late 1930s. They altered the heating chamber and eliminated the recessed well, which was hard to clean. Their improved design of plated metals, styled by industrial designer Alfonso Iannelli, became the famous Sunbeam Coffeemaster line of automated vacuum coffee makers (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.
Based on a successful series of commercial coffee brewers using the pourover, water displacement method of drip operation, Bunn entered the home consumer market with a different type of automatic drip-brew machine. In this type of coffeemaker, the machine uses a holding tank or boiler pre-filled with water. When the machine is turned on, all of the water in the holding tank brought to near boiling point (approximately 200-207 •°F or 93-97 •°C) using a thermostatically-controlled heating element. When water is poured into a top-mounted tray, it descends into a funnel and tube which delivers the cold water to the bottom of the boiler. The less-dense hot water in the boiler is displaced out of the tank and into the a tube leading to the spray head, where it drips into a brew basket containing the ground coffee. The pourover, water displacement method of coffeemaking tends to produce brewed coffee at a much faster rate than standard drip designs. Its primary disadvantage is increased electricity consumption in order to preheat the water in the boiler. Additionally, the water displacement method is most efficient when used to brew coffee at the machine's maximum or near-maximum capacity, as typically found in restaurant or office usage.
Artice Source: http://www.articlesphere.com
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