How an Espresso Machine Works

An espresso is a beverage made by forcing water heated to just below the boiling point through a filter of tamped, finely ground coffee beans. A single serving of espresso is a 1.25 to 1.5 ounce coffee concentrate topped with a thin layer of foam (referred to as the crema). Valued for its rich body and aromatic flavor, the espresso's bittersweet taste lingers on the palette after each sip, resulting in flavor satisfaction for coffee lovers.

While possible to construct a crude brewing method by forcing boiling water through coffee grounds using the force of steam, a specialized machine is needed to brew the ideal shot of espresso. An espresso machine heats the water to the recommended temperature, controls the water's pressure, and may even offer a steam wand attachment to heat and froth milk to add to the beverage.

The typical home espresso machine has a reservoir where cold water is poured. There is also a removable handle connected to a filter (called a porta-filter), which is just above the platform where the espresso cup is placed. When the machine is turned on, the water from the reservoir is pumped into a heating element. Once this element heats the water to the desired temperature (around 190 degrees Fahrenheit), an indicator light informs the user the brewing process is ready to begin.

Before brewing, the user fills the porta-filter with ground coffee and tamps the grounds. The porta-filter is then put into the machine and locked in place. A switch is flipped by the brewer that signals the machine's pump to pressurize the heating chamber to around 220 psi, forcing the hot water out of the heating element, through the coffee grounds, and out the spout on the bottom of the porta-filter. Once the cup is filled, the espresso machine is switched off and a fresh cup of espresso is ready to be enjoyed.

Although most espresso machines use this basic process to brew espresso, prices can range from fifty dollars to thousands. Some of the added features found in the more expensive units are the ability to moisten the grounds before the infusion process begins, higher grade pumps able to produce greater sustained pressures, beefed up heating systems, integrated water filters, and frothing wands.

Achieving a good cup of espresso from a home machine does not have to cost thousands of dollars, though. Simple procedures can add to the flavor of the espresso even in lower end machines. Filling the reservoir with filtered water will keep unwanted chemicals out of the brewing process. The type of coffee bean and fineness of the grind has a direct impact on the overall flavor and should be experimented with to discover the perfect blend. Also, adjusting the compactness of the grounds in the porta-filter affects the emulsion process, the results of which are visible in the crema. Perhaps the most important quality of a good espresso is freshness. Using fresh grounds will ensure the full taste of the coffee comes through. The espresso should also be consumed within a couple of minutes of brewing to experience its full flavor.

With a little experimentation, the same quality ordered at a cafe can be enjoyed at home using a home espresso brewer. The satisfaction of having perfectly brewed your own espresso, however, will never be found on a Starbuck's menu.