How Does Machine Espresso Work?

The machine espresso makes use of precision pressure, and a filtering system that is awe-inspiring to make the coffee you enjoy. What exactly is it that makes it work?

Espresso is created by forcing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure.

The Head of the Group

As the name implies, the group head is the place you place your portafilter while brewing espresso. It disperses water into the portafilter, and regulates the pressure during the extraction. There are various kinds of group head, each with their particular advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion options, and others are designed to control the lever. There are even some that contain a variety of features, like the E61, which is considered the most popular choice among baristas for its ability to provide multiple benefits in a single package.

As you can see from the above photo the head of the group is fitted with several notches. You place your portafilter in these notches, then turn the head around to secure it. A gasket of rubber is situated inside the notches to help create a seal when you insert your portafilter. The notches allow for the precise placement of the portafilter. This is crucial to ensure a consistent extraction.

The group head does not just allow you to place your portafilter easily however, it also keeps a constant temperature. It does this by cycling hot water through the brew pan and around the portafilter, making sure that it’s always at the correct temperature to extract. It is crucial to keep in mind that even a tiny differences can make the distinction between a great and a great espresso.

The Pump

Contrary to manual piston machines which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure required for espresso extraction. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are typically more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and inadequate cleaning. They also create mechanical complexity that can lead to costly prices for even the most basic models.

Some espresso machines employ steam pressure instead of a pump for brewing espresso machines for home. This can result in over-extraction because the boiler that makes steam also warms the water to boil. Additionally these machines are often required to restore their pressure between cups, which requires time and energy.

Many espresso machines employ either a rotary or vibration pump, with a vibrating model that uses a vibrating disc to generate the pressure, and an rotary model that pushes hot water through the grounds under high speed. Both types of machines can produce an excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the one that is used to heat the water to the ideal temperature to extract. The steam that is created gets to the portafilter which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process the steam is able to create enough pressure to push the grounds of coffee through. This creates a foam on the top of the espresso. This is a hallmark of a great espresso.

There are three types of cheap espresso machine machines, each with different pumps and brew temperature. There are also different ways in which the brew could be controlled and the size of the cup the machine is capable of making.

The first espresso machines were steam-types. They used one boiler to make steam and brew, however, the pressure they could create was minimal – two bars of atmospheric pressure at the most. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso maker is a semi-automatic device with an electric espresso maker pump. This is what people envision when they think of an espresso machine. With a semi-automatic espresso machine, you grind the beans and then tamp them yourself but the pump provides regulated water flow and pressure. This is a great compromise between the human touch and the mechanized consistency.

The Filter

Typically, espresso machines use filters that separate the grounds of the coffee as they go through the hot water. The filter is also an essential component of the temperature control system, since it helps prevent the machine from overheating.

It also improves flavor, since a filter can allow for a longer bloom phase. This allows the beans to release their nuances, and also allows for better extraction.

However it is crucial to remember that even a top filter could result in a bad cup of coffee, as the quality of the beans and extraction are essential.

This is where the magic happens, it’s the thing that makes an espresso really taste great. The grouphead, often referred to as the brewhead, is where the portafilter (the container you place the coffee ground into) sits when you’re making espresso.

In a steam-driven espresso machine hot water is heated in an airtight tank to produce steam, which is then pushed through the grounds with high pressure. These types of machines are generally less expensive and simpler to maintain than pump-driven models. They are however limited in their ability to create the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, compressed air-driven espresso machines have become more popular. They use an air compressor to force the hot water through the grounds, and are far more portable than steam-driven Electric espresso maker machines.