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How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to make the delicious coffee we enjoy. What exactly is it that makes it work?

To make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However, it is the pressure that makes the main difference.

The Group Head

The group head is the portafilter that you place in the espresso maker when making it. It disperses the water into the portafilter and regulates the pressure of extraction. There are a variety of types of group head each with its unique advantages and disadvantages. Some are designed for temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. There are also some that come with a range of features, such as the E61, which is the most popular choice among baristas for its ability to offer multiple benefits in a single package.

As you can see in the above photo The group head features many notches in which you can put your portafilter, then twist it by hand to lock it in. There is also a rubber gasket that is a part of the notches, which helps create the seal when you insert your portafilter into the machine. The notches allow for precise placement of the portafilter. This is crucial for an efficient extraction.

In addition to allowing you easily place your portafilter in, the group head is also responsible for maintaining an even temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, making sure that the temperature is always at the right level to extract the coffee. This is important because even a small difference in temperature can make the difference between good and great espresso.

The Pump

Unlike manual piston machines, which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure that are required for espresso extraction. The pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger before it is shot through the ground coffee inside the group head.

Pumps are typically less expensive than piston-driven models, and they tend to last longer, however both types of machines could get damaged through overuse and lack of cleaning. Pumps are also more complex mechanically, which could increase the cost of even simplest models.

Some espresso machines make use of steam pressure instead of a pump to brew espresso. This can cause over-extraction because the boiler that makes steam also heats the water to boil. The machines must also continually rebuild their pressure between cups. This takes energy and time.

Many espresso machines make use of an rotary or a vibration pump. A vibration model utilizes the vibrating disk to create pressure, whereas the Rotary model pushes hot coffee through the ground at a fast speed. Both types of machines can produce an excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the one that is used to heat the water to a temperature that is ideal for extraction. The resulting steam is then transferred to the portafilter which holds ground espresso beans and is then funneled down into the cup. The steam causes pressure to push through the coffee grounds. This results in a layer of crema that is then poured over. This is a hallmark of a great espresso.

There are three kinds of espresso makers, and they differ in the type of pump they employ and the degree of heat that the brew is. There are various ways that the brew may be controlled as well as the size of the cup that the maker can create.

The first espresso machines were steam-type. They had one boiler to create both 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 tasting burnt and bitter. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso machine is a semiautomatic with an electric pump. These are the things people think of when they imagine an espresso machine. With a semi-automatic machine, you must grind the beans and tamp them by hand, but the pump is able to regulate the flow of water and pressure. This is an excellent compromise between human touch and the mechanised accuracy.

The Filter

Typically, espresso machines have filters that separate the coffee grounds as they pass through the hot water. The filter is also a vital element of the temperature control system, as it keeps the machine from overheating.

A filter also improves flavor because it allows for an extended flowering time. This lets the beans release their nuances, and also allows for better extraction.

However, it is important to remember that even a good filter can result in a poor cup of coffee, since the quality of the beans and extraction is vital.

This is where the magic happens, and it's what makes an espresso really taste good. The grouphead (also called the brewhead) is where you place the portafilter, the thingy that you put the grounds of coffee into while making espresso.





Steam-driven espresso machines use hot water heated in an airtight container to make steam. The steam then pushes hot water into the grounds of coffee at high pressure. They are less expensive and easier to maintain than pumps-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, espresso machines powered by a compressed air pump have become increasingly popular. They utilize an air compressor to force hot water into the grounds, and are far more portable than steam-driven electric machines.