How Does Machine Espresso Work?

Machine professional espresso machine utilizes precise pressure and mind-blowing filter technology to make the coffee we love. What exactly does it work?

Espresso is created by forcing hot water under 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 suggests, the group head is the place you place your portafilter while making espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the resulting extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some focus on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. There are some that include a mix of features, such as the E61, which is considered to be the most popular among baristas because of its ability to offer multiple perks in one package.

As you can see from the above photo the head of the group is fitted with a variety of notches. The portafilter is placed in these notches, then turn the head around to secure it. There is also a rubber gasket in the notches and helps create a seal when you insert your portafilter into the machine. The notches on the head allow for a precise placement of the portafilter, which is crucial to ensure an efficient extraction.

The group head not only allows you to insert your portafilter easily however, it also keeps the same temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure the temperature is always right for extraction. This is crucial, since just a few degrees could make the difference between a good and excellent espresso.

The Pump

Unlike manual piston machines, that use a lever to pressurize water, rotating espresso machines rely upon motorized pumps to provide the nine atmospheric bars of pressure necessary to extract espresso. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be less expensive than piston-driven machines and tend to last longer, although both types of machine can become damaged due to excessive use and poor espressomachines cleaning. Pumps are also more complicated mechanically, which can increase the cost of even most basic models.

Some espresso machines can eliminate the pump completely and instead make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that produces steam also causes the water to boil. The machines also need to constantly rebuild their pressure between cups. This requires energy and time.

Many espresso machines utilize an rotary or vibrating pump, which has a vibration model using a rotating disc to generate the pressure, and an rotary model that pushes hot water through the grounds under high speed. Both machines produce great espresso, however rotary machines are quieter, more durable and less likely to fail.

The Boiler

The boiler is the one that makes the water warm to the ideal temperature for extraction. The resulting steam reaches the portafilter which holds ground espresso beans and gets funnelled down into the cup. During this process, the steam creates pressure and pushes through the coffee grounds. This creates a foam on the top of the espresso. This is one of the main characteristics of a great espresso.

There are three distinct types of espresso machines, each with different pumps and brew temperature. There are various ways to control the brew as well as the size of cup that can be made by the machine.

The first espresso machines were steam-based. They had one boiler to create steam and brew, but the pressure they could produce was not very high - two bars of atmospheric pressure, at most. This resulted in the coffee and espresso maker tasting bitter and burnt. This is the reason Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most commonly used espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic machine you need to grind the beans and tamp them yourself but the pump provides regulated water flow and pressure. This is an excellent compromise between human control and mechanised reliability.

The Filter

Espresso machines usually have a filter that separates the grounds of the coffee from hot water. The filter is also an essential component of the machine's temperature control, as it prevents overheating.

Filters also aid in flavor, as it permits an extended flowering time. This allows beans to release their flavors and provides an opportunity for a better extraction.

It is important to remember that even the best filter can make a bad cup of coffee. The quality of the beans, and the extraction process remain crucial.

It's here that the magic occurs. This is what makes espresso taste so delicious. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you put the grounds of your coffee into while making espresso coffee machine for home.

Steam-driven espresso machines make use of hot water heated in an airtight container to make steam. The steam then moves hot water through the coffee grounds under high pressure. These kinds of machines are generally less expensive and simpler to maintain than pump-driven models. However, they are limited in their capacity to create the ideal conditions for brewing as they only operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.

In recent years, compressed air-pump-driven espresso machines have become more popular. They make use of an air compressor to push hot water through the ground and are more mobile than electric steam-driven espresso machines.