How Does Machine Espresso Work?

Machine espresso uses precision pressure and incredible filter technology to produce the delicious coffee we enjoy. But how exactly does it work?

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

The Head of the Group

As the name implies the group head is where you put your portafilter in when making espresso. It disperses water into the portafilter and regulates the pressure of extraction. There are numerous kinds of group heads, each with its own advantages and drawbacks. Some are specifically designed for stability of temperature while others are built to handle pre-infusion. Some are designed to control the lever. There are even some that come with a range of features, such as the E61 one, which is to be the most popular among baristas due to its capacity to offer multiple perks in a single package.

As you can see in the above photo the group head is made up of several notches where you put your portafilter, then twist it manually to secure it. There is also a gasket of rubber in the notches to help create an airtight seal when you insert your portafilter into the machine. The notches on the head permit an exact position of the portafilter which is vital for an even extraction.

In addition to allowing you to easily insert your portafilter, the group head is also responsible for maintaining an even temperature. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring the temperature is always right to extract the coffee. This is crucial, since even a few degrees can mean the difference between good and excellent espresso.

The Pump

Unlike manual piston machines, which use a lever to pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure required to extract espresso. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being shot through the ground coffee inside the group head.

Pumps tend to be 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, which can result in a high price tag on even the simplest models.

Some espresso machines eliminate the pump completely and instead make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that produces steam also causes the water to boil. Additionally, these machines frequently have to rebuild their pressure between cups, which takes time and energy.

Many espresso machines utilize an rotary or vibrating pump, which is a vibration model using a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds under high speed. Both types of machine are capable of producing excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the element that heats the water to the optimal temperature for extraction. The resulting steam reaches the portafilter containing ground espresso beans and is then pumped into the cup. In this process, the steam creates pressure to push through the coffee grounds. This results in a layer of crema on top. This is one of the hallmarks of a great espresso.

There are three types of espresso makers, which differ in the kind of pump they use and the degree of heat that the espresso is. There are a variety of ways to control the brew and the size of cup that can be produced by the machine.

The first espresso machines were steam-type. The first espresso machines were steam-type machines. This led to the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized quality.

The Filter

Espresso machines usually have filters that separate the grounds of the coffee from the hot water. The filter is also a crucial part of the temperature control system, as it keeps the machine from overheating.

A filter also helps with flavor because it allows for the beans to flower for a longer period of time. This helps the beans to release their flavor and gives an opportunity for better extraction.

It is important to keep in mind that even the best filter can result in a bad cup of coffee. The quality of the beans, as well as the extraction, remain crucial.

This is where the magic happens, it's the thing that makes espresso taste good. The espresso machines home grouphead (also known as the brewhead) is where you place the portafilter, which is the thingy that you put the coffee grounds into, when making espresso.

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

In recent times, espresso machines powered by compressed air-pump have become increasingly popular. They utilize an air compressor to push hot water through the grounds and are more portable than steam-driven electric machines.