How does an espresso machine work?

At first glance, espresso machines seem quite complex, but the structure and operating principle are easy to understand. We explain how an espresso machine works and how it is built.

The functional principle

The special feature of an espresso machine is that the water is pressed through the espresso powder at a pressure of 9 bar. Due to this high pressure, the coffee powder comes into contact with the water for about 25 seconds. Therefore, several conditions must be met for the espresso to succeed:

  • The espresso beans must be finely ground (freeness 2 to 3) so that the water can absorb enough aroma in the short time. The finer the beans are ground, the larger the contact surface and the more flavor the water can absorb.
  • The espresso powder must be pressed down well so that it can not fly around as soon as the water hits it. Coffee mills are often equipped with a tamper for pressing the espresso powder. However, since you are only pressing the portafilter from below, you can not exert sufficient force here. We recommend that you buy a rubber mat and a stainless steel tamper. So you can support the filter holder on the rubber mat and press the tamper briefly but vigorously the espresso powder.
  • The espresso powder in the filter holder must be evenly distributed so that no channels are formed. To do this, fill the portafilter with espresso powder to the brim and rub down the excess powder with one finger without pressing on the powder!

There are also espresso machines, where the pressure is adjustable, even beyond 9 bar. This is more for coffee professionals who like to play with taste. In general, 9 bar is the optimum pressure.

The construction of an espresso machine

The pressure is usually generated by an electric pump. This transports 90 to 95° C hot water to the brewing group, where the filter holders are attached.
Furthermore, a good espresso machine has a steam lance used to froth the milk and a spout for hot water, e.g. to prepare a tea or an espresso coffee. These two outputs are either connected to the same kettle (single-circuit) or have a separate water circuit (two-circuit) or even a separate boiler (dual boiler), because the water temperature required here is 120 to 130° C. Find out more about single-circuit, dual-circuit and dual-boiler here.

Tips & Tricks

Experiment a little with your espresso machine: just lightly press the espresso powder and once exaggerate it. You will undoubtedly notice the difference in the taste of espresso!

Video Board: How it Works: Deep Inside a Cutaway Espresso Machine