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Brewing Coffee

There are several different methods of brewing coffee, each resulting in a different strength and flavour of coffee. The following points should be observed:

Manual filter - one of the most basic of brewing methods, preferred by many connoisseurs since they can control every aspect of the process. Basically it involves pouring hot water into a filter containing the coffee, which then drips into the cup or carafe. The resulting coffee is dependent on the water quality and temperature; the type of coffee bean, roast and grind; the ratio of coffee to the water; and the filter type. Good quality gold type single cup filters are readily available and produce a good cup of coffee with a wide variety of coffee blends. Filtered water at about 95°C (or 200°F - just below boiling) produces the best result. The fine filter allows a very fine grind of bean to be used, resulting in fast brewing. The first (paper) filter was invented by German housewife Melitta Bentz in 1908. These filters were flat and round - the modern "fast" conical filter system was introduced by Melitta in 1937.

Presso/French Press/Plunger - another simple method of coffee brewing similar to brewing tea with leaves (which can be done the same way). The "French" press was actually invented by an Italian named Calimani in 1933. Hot water is poured into a beaker (just like a lab beaker) containing the ground coffee and is allowed to brew for about 4-6 minutes. Once the coffee is brewed a plunger with a filter at the end is pushed down to separate the grounds and end the brewing. Again the main variables are the quality of the filter (usually a metal mesh); the coffee itself; and water temperature and quality. The main drawback is the time taken to brew the coffee - a result of the courser grind of coffee required - which allows the water to cool below the optimum temperature. Thermal (insulated) plunger units and insulated jackets which keep the coffee warm are now available.

Percolator - this is the stereotypical American method of brewing coffee. It consists basically of a coffee pot with a narrow tube leading from the bottom of the pot to a filter basket at the top containing the grounds. As the water in the pot boils water is forced up the tube and into the basket, percolating down to be heated again until the coffee is brewed to the desired strength. The main drawback to this system is the continued boiling and cycling of the coffee while it is brewing (prolonged by the very course grind required), resulting in the loss of some of the more volatile flavours and a more bitter, burnt taste. A wide range of percolators are available, from stovetop/campfire models to fully automatic electric models which will brew the coffee and then keep it warm. The first electric percolator was introduced by 1908 and both urns and pots were available by 1914. Farberware introduced their classic electric percolator in 1930, and the first automatic model in 1937. Presto added a removable control in 1958 - allowing the pot to be immersed when cleaning (removable plugs were common in the 30's).

Vacuum Pot - invented in 1840 by Scottish marine engineer Robert Napier, the vacuum pot uses a process similar to percolators and siphon coffee makers. The vacuum pot consists of two detachable glass globes. The lower globe contains a tube like a percolator and connects to a filter in the upper globe which contains the coffee. As water in the lower globe boils the vapor pressure forces it into the upper globe where the coffee then brews. When the pot is removed from the heat the air in the lower globe cools, creating a partial vacuum which sucks the brewed coffee down through the filter and back into the lower globe. The top globe is then removed and the coffee poured out of the lower globe. The process is spectacular but the devices are relatively fragile, and very few are made today. Bodum, famous for its presso coffee makers, introduced its Santos model in 1958.

Electric Drip Filter/Percolator - there are two basic varieties - automatic, which has a permanent water supply connected; and pour-over (invented by Bunn-O-Matic in 1963), which has water poured in. Both typically have a reservoir, a water heater, and a tube leading to a head which distributes hot water over a filter basket containing the coffee. Unlike a percolator the coffee brew is not continuously boiled and percolated, but drips into a server, usually a carafe of some kind. Drip filter machines are the most varied of all types, accommodating a large range in size and servers, from single cup models through warmed glass carafes to giant commercial models with multiple thermal carafes or heated removable servers. Different models use different techniques for distributing the hot water through the coffee and getting the right water temperature (around 95°C/200°F) for the best flavour brew. Many types use a a method similar to a percolator (as water in the reservoir boils it is forced through the tube to spray over the filter), producing the same characteristic noise. Other factors affecting the flavour are the quality of the water (automatic models often have a water filter in the supply pipe) and the type of coffee filter (disposable paper, metal mesh, or fine gold type). Drip filter machines can use a very fine grind of coffee and produce a much better flavour coffee than a percolator.

Espresso Machines - espresso coffee refers not to speed, but to a method of forcing water through the coffee at high pressure in order to extract the full flavour. Espresso coffee is therefore very strong and usually served in small "demitasse" glasses, or mixed with a large amount of milk as in a latte or cappuccino. The first espresso machine was invented by Bezzera in 1901, and produced by the Italian company La Pavoni in 1905. These early machines used steam pressure to force boiling water and steam through the filter containing the coffee. The high temperature of the water and the steam resulted in a burnt flavour, and in 1938 a new method was introduced. This used a heat exchanger to produce hot (not boiling) water forced through the coffee by a piston pump, and produced the rich froth or crema now characteristic of espresso. The first commercial models were produced by Gaggia in 1946 (after WW2). The high pressure (9-10 atmospheres) produced by the piston caused its own problems for the operator, who had to force the piston down with a lever. This inspired first hydraulic assistance (using a second piston the operator could produce the same pressure with less force) and ultimately an electric pump - introduced by FAEMA in 1961. Not only did the electric pump make the machine safer and easier to use, but it also enabled the development of completely automatic machines, which can produce espresso at the touch of a button. Most modern machines use the heat exchanger and electric pump, although some people still prefer the lever operated piston pump. The complexity of an espresso machine makes them far more expensive than a good drip filter machine, and so home machines are not as common.

Stove-top Espresso/Italian Coffee Maker - the cheapest and most popular method of making espresso, pretty close to what the early Bezzera and La Pavoni machines produced. This coffee maker has two sections (like a vacuum pot) which screw together. The lower (boiler) section works like a pressure-cooker (with a safety valve), with a filter basket containing the coffee grounds. As pressure builds in the lower section water and steam are forced through the grounds and then through another filter at the bottom of the top section. The brewed coffee is forced through a tube and out a valve (which keeps the pressure high) into the pot. Like early espresso machines the high temperatures tends to result in a burnt flavour, but then these devices are only a tenth of the cost of a home espresso machine. The first stove-top espresso maker was developed in 1933 by Alfonso Bialetti, and has been in production since the 1950's (over 200 million have been produced). It was inspired not by the similar vacuum pot, but by the heater for a washing machine!! Bialetti recently introduced its "Sistema Brikka" which produces the crema characteristic of espresso machines. A variety of designs are available (including electric versions), most from a number of Italian makers (many copies of Bialetti designs).

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