Espresso machines may be steam-driven, piston-driven, pump-driven, or air-pump-driven. Machines may be manual or automatic. An espresso machine brews coffee by forcing pressurized water near boiling point through a puck of ground coffee and a filter.
The first machine for making espresso was built and patented in 1884 by Angelo Moriondo of Turin, Italy. An improved design was patented in 1901, which was bought by the founder of the La Pavoni company which from 1905 produced espresso machines commercially on a small scale in Milan.
Multiple machine designs have been created to produce espresso. Several machines share some common elements, such as a grouphead and a portafilter. An espresso machine may also have a steam wand which is used to steam and froth liquids, to include milk, for coffee drinks such as cappuccino and caffe latte.
Moka pots, also known as stove top espresso makers, are similar to espresso machines in that they brew under pressure and the resulting brew shares some similarities, but in other respects differ. As such, their characterization as espresso machines is at times contentious, but due to their use of pressure and steam for brewing, comparable to all espresso prior to the 1948 Gaggia, they are accepted within broader uses of the term but distinguished from standard modern espresso machines.
Multiple machine designs have been created to produce espresso. Several machines share some common elements. Varying the fineness of the grind, the amount of pressure used to tamp the grinds can be used to vary the taste of the espresso. Some baristas pull espresso shots directly into a pre-heated demitasse cup or shot glass, to maintain a higher temperature of the espresso.
A steam-driven unit operates by forcing water through the coffee by using steam or steam pressure. The first espresso machines were steam types, produced when a common boiler was piped to four group heads so that multiple types of coffee could be made at the same time. This design is still used today in low-cost consumer machines, as it does not need to contain moving parts.
The piston, or lever, driven machine was developed in Italy in 1945 by Achille Gaggia, founder of espresso machine manufacturer Gaggia. The design generically uses a lever, pumped by the operator, to pressurize hot water and send it through the coffee grinds. The act of producing a shot of espresso is colloquially termed pulling a shot, because these lever-style espresso machines required pulling a long handle to produce a shot.
There are two types of lever machines; manual piston and spring piston design. With the manual piston, the operator directly pushes the water through the grounds. In the spring piston design, the operator works to tension a spring, which then delivers the pressure for the espresso usually 8 to 10.
A refinement of the piston machine is the pump-driven machine, which was introduced in the Faema E61 in 1961, and has become the most popular design in commercial espresso bars. Instead of using manual force, a motor-driven pump provides the force necessary for espresso brewing.Espresso machines are made to accept water directly from a cold water line supply, common in commercial installations, or from a separate tank that must be filled with water by hand. The latter is more common with lower-volume commercial installations and domestic espresso machines. Due to the required high pumping pressure and precision flow control needed, the particular type of electric pumps typically used are known as ‘solenoid-piston’ pumps.
Espresso machines are made to accept water directly from a cold water line supply, common in commercial installations, or from a separate tank that must be filled with water by hand. The latter is more common with lower-volume commercial installations and domestic espresso machines. Due to the required high pumping pressure and precision flow control needed, the particular type of electric pumps typically used are known as ‘solenoid-piston’ pumps. These pumps are classified as a positive displacement type (general category) of pump.
In recent years air-pump driven espresso machines have emerged. These machines use compressed air to force the hot water through the coffee grounds. The hot water is typically added from a kettle or a thermo flask. The compressed air comes from either a hand-pump, N2 or CO2 cartridges or an electric compressor.One of the advantages of the air-pump driven machines is that they are much smaller and lighter than electric machines. They are often handheld and portable. The first air-pump-driven
One of the advantages of the air-pump driven machines is that they are much smaller and lighter than electric machines. They are often handheld and portable. The first air-pump-driven machine was the AeroPress, which was invented by Alan Adler, an American inventor, and introduced in 2005. Handpresso Wild, invented by Nielsen Innovation SARL, a French innovation house, was introduced in 2007.
A grouphead (or group head) is the receiver for the removable portafilter (or group handle). A typical consumer espresso machine normally has only one grouphead, while popular professional machines, such as those used at commercial coffee shops, can contain anywhere from one to seven. During the process of extracting a shot of espresso, hot water is forced through the grouphead under pressure. The grouphead contains many holes (the shower) that attempt to distribute the pressurized water evenly over the surface of the grinds in the portafilter basket and thereby achieve an even cross sectional flow.
A portafilter (or group handle) attaches to the grouphead of semi-automatic and piston-driven espresso machines, and carries a tamped puck of coffee grounds within its basket. It is usually made of brass for better heat retention, and is attached by a plastic or wooden handle. The portafilter forms a seal with the espresso machine’s gasket, and directs high-pressure hot water through the coffee puck. After-market retailers also sell bottomless portafilters that minimize the espresso’s contact with any metal.
A bottomless portafilter is one tool baristas use to analyze the quality of the coffee grind and the evenness of the extraction and allows for a visual check of channeling or the condition in which water is able to pierce a hole in the espresso puck during the brew process leading to poor extraction. Often, baristas use knockboxes to store their spent espresso grounds after they have pulled a shot.