Espresso machine
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An espresso machine is used to produce the traditionally Italian coffee beverage called espresso.
An espresso machine forces water at 90 °C (195 °F) and 9 bar of pressure through a puck of finely ground coffee. This process produces a rich, almost syrupy beverage by extracting and emulsifying the oils in the ground coffee. An ideal double shot of espresso should take 20-25 seconds to arrive, timed from when the machine's pump is first turned on. This time can be tuned by using finer or coarser ground coffee, and by altering the tamping pressure.
An espresso machine also has a steam wand which is used to steam and froth milk for milk based espresso beverages such as the cappuccino and latte.
A professional operator of such a machine is called a barista.
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Types of espresso machines
Stovetop espresso maker
Commonly found in Italy, stovetop espresso makers produce a dark coffee almost as strong as that from a conventional espresso maker. A small cup that screws into the body of the maker holds the water, which when heated, forces its way up through the coffee grounds held in a small cup of the maker. The coffee then works through a small tube and into the coffee pitcher. They are known colloquially as moka pots, after an early trademark.
Stovetop espresso makers are conveniently portable, since they require no electricity to use. This makes them great for tourists and hikers. While stovetop espresso makers produce dark coffee, the coffee usually lacks the fine crema produced by conventional espresso makers.
Steam Espresso Maker
Similar to a stovetop espresso maker, a steam unit operates solely by steam pressure, but is fashioned more in the style of a typical pump-powered unit, including the filter-holding/coffee dispensing head called a portafilter. Steam units generally produce a product more or less identical to a stovetop espresso pot.
Piston-driven Espresso Maker
Now mostly characteristic of the showpiece high-end designs of La Pavoni, the piston-driven espresso maker is the archetype of the modern espresso machine, and the origin of the crema, which was originally thought to be an undesirable waste product but is now considered characteristic of a properly made shot of espresso. It was invented in 1938 by Achille Gaggia; while it is still considered a good way to make espresso, it requires some strength to operate, and most such units sold today are as much showpieces as practical devices.
Pump-Driven Espresso Machine
A refinement of the piston machine is the pump-driven machine, which has become the most popular design in commercial espresso bars. Instead of using manual force, a pump is used with a boiler in most designs. Commercial and high-end home designs often use a built-in shot timer; low-end pump machines measure the shots manually, requiring the use of a graduated shot glass or similar container to measure the proper amount of coffee. High-end machines are often attached directly to the plumbing of the site; low-end machines have built-in water reservoirs. A refinement of the design created originally by the German firm Krups called the thermoblock eliminates the boiler in favor of a heat exchanger that heats the water as it's pumped; though considered technically superior from a design standpoint, implementations of the design have traditionally been lacking.
Automatic Espresso Machine
Becoming increasingly common in both home and commercial settings, automatic espresso machines, though significantly more expensive than pump machines, tend to produce a more consistent product with less fine-tuning than the pump-driven machines, completely automating the entire process from grinding the beans to disposing of the spent coffee grounds. All automatic units are pump-driven units of either the standard or thermoblock variety.
External links
- Consumer reviews of many espresso machines, grinders and tampers (http://www.coffeegeek.com)
- TooMuchCoffee: The European Coffee and Espresso Resource. Non-commercial, with reviews and lots of info on espresso machines and grinders. (http://www.toomuchcoffee.com/)