Espresso Machines

 Piston-driven Espresso Machine

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 bar).

The piston-driven machine is 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.

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