How Does Machine Espresso Work?

Machine espresso employs precise pressure and amazing filter technology to make the coffee we love. How exactly does it work?

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

The Group Head

The group head is the portafilter that you place in the espresso maker when making it. It distributes water into the portafilter, and regulates the pressure during the extraction. There are numerous kinds of group heads, each with its own advantages and disadvantages. Some focus on temperature stability, others on pre-infusion capabilities, while others are designed to control the lever. There are also some that include a mix of features, like the E61 one, which is the standard choice for many baristas due to its ability to provide multiple benefits in a single package.

As you can see from the photo above, the group head is equipped with several notches. The portafilter is placed in these notches, then turn the head around to secure it. A gasket made of rubber is positioned inside the notches, which helps create a seal when you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is crucial to ensure an even extraction.

Apart from allowing you easily insert your portafilter, the group head is responsible for maintaining a consistent temperature. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring the temperature is always right for extraction. This is vital, because even a few degrees can be the difference between a good and excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, rotating espresso machines rely upon motorized pumps to provide the nine atmospheric bars of pressure required for espresso extraction. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger prior to it is shot through the ground coffee in the group head.

Pumps are generally less expensive than piston-driven machines and tend to last longer, but both types of machines may be damaged by excessive use and inadequate cleaning. They also add mechanical complexity, which can result in an expensive price for even the most basic models.

Certain espresso machines utilize steam pressure instead of a pump for brewing espresso. This can result in over-extraction because the boiler that makes steam also heats the water to boil. Additionally these machines are often required to rebuild their pressure between cups, which takes time and energy.

A majority of espresso machines utilize the rotary or vibration pump. A vibration model utilizes a rotating disk to generate pressure, while the circular model pushes hot liquid through the ground at a rapid speed. Both machines can make great espresso, however rotary machines are quieter, more durable and less likely to break.

The Boiler

The boiler is the element that heats the water to the ideal temperature for extraction. The steam produced is then directed to the portafilter, which contains the espresso coffee grounds. It is then pumped into the cup. The steam causes enough pressure to push the coffee grounds through. This results in a layer of crema that is then poured over. This is one of the main characteristics of a good espresso.

There are three kinds of espresso machines, each having different types of pumps and brew temperature. There are also different ways in which the brew could be controlled as well as the dimensions of the cup the maker can create.

The earliest espresso machines were steam-based. They had a single boiler to make both brew and steam, espresso maker however, the pressure they could produce was not very high - two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso maker is a semi-automatic device with an electric pump. When people think of professional espresso machine machines, they envision these machines. With a semi-automatic machine you grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is an excellent compromise between human control and mechanized reliability.

The Filter

Espresso machines usually use filters that separate the grounds of the coffee from the hot water. The filter is also an essential part of the machine's temperature control, since it helps to prevent overheating.

It also helps with flavor, as a filter allows for a more prolonged bloom time. This helps the beans let their nuances out and provides the chance for better extraction.

It is important to keep in mind that even the finest filter could result in a poor cup of coffee. The quality of the beans, as well as the extraction, remain vital.

This is where the magic happens. It's what makes espresso taste great. The grouphead (also known as the brewhead) is where you place the portafilter, which is the thingy which you put the grounds of coffee into while making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These types of machines are usually less expensive and easier to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, compressed-air-pump-driven espresso machines have been gaining popularity. They use an air compressor to force hot water into the grounds and are significantly more portable than electric steam-driven machines.