Coffee

The flavors in coffee are extracted by hot water, and there are a number of ways by which to extract these flavors. The coffee must be ground for all of these methods -- just as the increased surface area contributes to faster degradation, it also allows the rapid extraction of flavor by water. There are two basic methods by which this is done, either by allowing the grounds to sit in hot water and steep like tea, or by forcing hot water through the grounds. Generally some combination of these two processes is done.

Brewing

On the one extreme is the French press. The grounds are placed into the bottom of a vessel and hot water is poured onto them. The mixture sits for a few minutes (A), then a mesh strainer is pushed down onto the mass (B) and the coffee (C) is poured off to drink.

The other extreme is espresso. A fine grind of strong coffee is packed into a small metal container with a hole in the bottom. Pressurized water is forced through the grounds, where it extracts a strong flavor, then falls into the pot below. Although some sources say that espresso is made with pressurized steam, no espresso machine actually works this way. The pressure is usually driven by some type of electric pump, but hand-operated pistons are also available.

In America, the most common brewing method is the drip method, which is halfway between these two. The grounds are placed in a basket with a non-reactive liner of paper or sometimes gold, with a small hole in the bottom. Hot water is poured over the grounds, where it soaks the grounds and steeps for a short time while being slowly forced by gravity through the hole into the container below where it is kept warm (or at least insulated) while the brewing process finishes.

In Italy, the most common method of brewing coffee is in a moka-style percolator. Water is placed in the lower section (A) and the raw coffee grounds in the mid-section (B) with the spout reaching below the water level level. After the top section, initially empty, is affixed, the pot is placed on a heat source. As the water reaches boiling point it turns to steam and eventually creates sufficient pressure to force all the water from the lower section up the tube at once, through the grounds — which are held in place by a metal filter above and below — and through a second tube until it hits the lid of the pot and is collected in the upper section (C), producing a strong, concentrated coffee. Gaskets and safety valves to ensure a tightly closed unit allow for pressure to safely build up in the lower section and provide a necessary security release if this pressure gets too high.

There are many factors in the final result. First is the roast and quality of the coffee beans. Freshly ground, newly roasted beans will always give a better cup of coffee than pre-ground, older beans. Clean fresh water is necessary, and the temperature of the water will have some bearing on the result. Cooler water will not extract flavors as efficiently as hot water, but boiling water can be a little too good with a very dark roast. Lastly, the coarseness of the grind and the ratio of grounds to water are also important, and vary according to the brewing method used.

A good rule of thumb for beginning brewers is to use the simple drip method. Use 2 Tablespoons of finely ground coffee for every 6-7 oz of fresh water. Bring the water just to a boil, then pour slowly over the grounds, stirring gently as you do. Stirring will result in the grounds retaining some extra water, but do not try to squeeze the water out. When it stops dripping, the coffee is ready to drink.