How Does Machine Espresso Work?

Machine espresso uses precision pressure and incredible filter technology to produce the coffee we love. How exactly does it work?

To make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.

The Group Head

As the name suggests, the group head is the place you put your portafilter in when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the extraction. There are several different types of group head, each with their particular advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. Some come with a combination of both, such as the E61. This is a favorite among baristas because it offers multiple benefits in one package.

As you can see in the image above, the group head has numerous notches that you can put your portafilter, then twist it with your hands to secure it. A rubber gasket is located within the notches to create a seal as you insert your portafilter. The notches on the head allow for an exact positioning of the portafilter which is necessary for an efficient extraction.

The group head does not just allow the portafilter to be inserted easily, but it also maintains an even temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is always at the right level to extract the coffee. It is important to realize that even a best small espresso machine deviation can make the difference between a good and great espresso.

The Pump

Motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure required for mini espresso maker extraction. This differs from manual piston machines that rely on levers. The pressure is created by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to it is shot through the ground coffee inside the group head.

Pumps are typically more affordable and last longer than piston-driven machines. However, both types of machines can degrade due to excessive use and insufficient cleaning. Pumps are also more complicated mechanically, and can add to the price of even the simple models.

Some espresso machines can eliminate the pump completely and utilize steam pressure to make espresso. This can cause over-extraction because the boiler that produces steam also warms the water to boil. Additionally these machines are often required to restore their pressure between cups, which takes time and energy.

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

The Boiler

The boiler is the one that will heat the water to the ideal temperature to extract. The steam that is produced is then directed to the portafilter, which contains the Espresso coffee machine for home coffee grounds. It is then poured into the cup. The steam is able to create enough pressure to push the coffee grounds through. This creates a layer crema on top. This is one of the main characteristics of a great espresso.

There are three types of espresso makers. They differ in the type of pump they use and how hot the espresso is. There are various ways in which the brew could be controlled as well as the dimensions of the cup the maker can create.

The first espresso machines were steam-type. They had one boiler to create steam and brew, however, the pressure they could generate was low - only two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most popular retro espresso machine maker is a semiautomatic machine that has an electric pump. This is what people envision when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the flow of water and pressure. This is an excellent compromise between human touch and the mechanized accuracy.

The Filter

Typically, espresso machines employ filters that separate the grounds of coffee when they pass through the hot water. The filter is also an essential component of the machine's temp control, as it helps prevent overheating.

It also helps with flavor, as a filter can allow for a longer bloom time. This allows the beans to let their nuances out and provides an opportunity for a better extraction.

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

This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead, often referred to as the brewhead, is where the portafilter (the thingy you put the ground coffee into) is located when you're making espresso.

Steam-driven espresso machines use hot water that is heated in an airtight container to make steam. The steam then pushes hot water through grounds of coffee under high pressure. They are less expensive and easier for the user to maintain than pumps-driven models. However, they are limited in their ability to produce 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 utilize an air compressor bean to cup espresso machine force hot water into the ground. They are also more mobile than steam-driven electric espresso machines.