It’s Tuesday morning and you are standing in line anxiously awaiting your AM latte. Loud hisses and hums are heard over the crowded noise of people conversing and ordering their beverages. A typical and familiar scene, you go about your business utterly unaware of the complicated powerhouse that is the espresso machine. The process of crafting the perfect shot of espresso can be broken down into four steps, each relying on a separate mechanism in the apparatus.
Perhaps as essential as the bean itself; water quality plays a crucial role in the making of rich, eye-opening espresso. Most commercial espresso machines are connected to a water line and rely on external filtration and softening systems. This constant water supply is ideal for high-volume, fast-paced businesses. Machines intended for light use rely on a reservoir, similar to a typical coffee brewer.
How is espresso made? With about 9 bars of pressure, that’s how! Equating to roughly 130 psi, crema bliss would be out of reach if it were not for this impressive mechanical heart. This is achieved in one of two ways.
The rotary pump is a mechanical method involving the use of a motor to spin a small, offset disk in a circular chamber. The disk is segmented by veins that press against the chamber wall when spinning. Water enters a section and becomes pressurized as it becomes more compressed due to the offset disk. This results in consistent pressure and quiet operation.
The vibratory pump utilizes a magnetic piston. This piston is set in a metal coil, and an electric current is run through the coil. This causes the piston to rapidly move back and forth, thus creating a pressure of about 60 pumps per second. While this type of pump may not last as long as its rotary cousin, it is both easier and more affordable to replace.
Trust us; temperature is every bit as important to good espresso as pressure and quality. And so, the boiler has an essential job; to consistently heat and hold pressurized water. Boilers are equipped with either a PID (proportional-integral-derivative controller) or a digital temperature control. These systems differ in regards to durability and price, but they both enable that cute barista to change and maintain the boiler water temperature.
And thus, we’ve come to the final step in the 20-second process of “pulling a shot”. Steam wands allow for the heating and frothing of milk for lattes and cappuccinos. The grouphead is the final stop for the now hot and pressurized water. There is a range of designs, but they all perform the same task; dispersing the water over a finely-ground and tightly-packed espresso “puck”.
While a fresh Americano may be the highlight of any coffee-lovers day, most drinkers are unaware of how much goes into their morning Joe. One may say the machine is as much a work of art as the espresso itself.