Brewed by the force and pressure of hot water through a finely ground blend of different beans, Espresso is a brew of concentrated coffee (best on a Gaggia 14101 classic espresso machine in my opinion!). Its beginnings are traced back to Milan, Italy, in the earlier part of the twentieth century, and tradition dictates that it be served in two-ounce shot glasses. The color itself is quite dark, and the consistency is thicker than that of regular coffee, with a small amount of cream, or froth, that sits on top of the espresso.
The beans used for brewing espresso typically consist of several varieties, but mainly Arabica beans. These beans spend more time roasting than basic coffee beans in order to extract as much of their oils as possible, after which they are ground to a very fine consistency, like that of powdered or confectioner’s sugar. How finely the beans are ground will impact the length of the brew; a typical brewing time is roughly thirty seconds on average.
Espresso machines come in a variety of shapes and designs and tinker with the processes behind making espresso, however, the same techniques are used to reach the result.
Historically, espresso makers are run using a pump driven by a motor to push a calculated amount of water necessary for a single shot of espresso through what is called a “thermo block”. The water is quickly heated and then pushed through the finely ground coffee. These machines are still the most popular today. This design can incorporate water via a built-in tank or can be piped directly into the plumbing of a building, with one or more heating chambers dedicated to the brewing of espresso and for the steaming wand, as each operate at separate temperatures.
Some people prefer using semi-automatic machines, which also use a motor, which drives a pump, however, the brew pressure is dispersed using a three-way valve. An automatic machine can input an exact measurement of water, allowing the pump to know when to stop and then disperse pressure via a three-way valve. A super automatic espresso machine will automatically grind the beans, evenly pack and distribute the grinds, brew the coffee, as well as froth, and afterwards add milk.
Modern machines have a control panel that is either back-lit with an LED display or something simpler, like an on/off light switch and a light that will signal when the water temperature is optimal for a shot of espresso. More expensive machines will have other extra features to give more information regarding the amount of pressure and water temperature and how it relates to the espresso it will produce.