How Does Machine Espresso Work?

The machine espresso is made using precision pressure, and filter technology that is mind-blowing to make the coffee you enjoy. But how exactly does it work?

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

The Group Head

As the name suggests, the group head is the place you put your portafilter in when making espresso. It distributes water into the portafilter and espresso machines regulates the pressure of the extraction. There are several different types of group heads, each with their particular advantages and disadvantages. Some are specifically designed for temperature stability while others are designed to handle pre-infusion. Others are made to control the lever. There are also some that come with a range of features, such as the E61, which is considered the classic choice among many baristas for its ability to offer multiple benefits in a single package.

As you can see in the image above the group head comes with several notches to place your portafilter and twist it by hand to secure it. There is also a gasket made from rubber that is a part of the notches and helps create the 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 for an even extraction.

Aside from allowing you to easily insert your portafilter, the group head is responsible for maintaining an even temperature. It does this by cycling hot water through the brew pan and around the portafilter to ensure that it's always at the correct temperature for extraction. This is important, as just a few degrees could make the difference between a good and excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure needed to extract espresso. This 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 in the group head.

Pumps tend to be cheaper and last longer than piston-driven machines. However, both types of machines can degrade due to overuse and insufficient cleaning. Pumps are also more complicated mechanically, which can increase the cost of even most basic models.

Some espresso machines remove the pump entirely and utilize steam pressure to make espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of the water to boiling which could lead to excessive extraction. Additionally these machines typically have to restore their pressure between cups, which takes time and energy.

Many espresso machines utilize an rotary or vibrating pump, with a vibration model using a rotating disc that generates the pressure, and the rotary model pushing hot water through the grounds under high speed. Both types of machines can make a great espresso, but 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 steam that is produced reaches the portafilter, which contains the ground espresso coffee, and gets funnelled down into the cup. In this process, the steam creates pressure to push through the grounds of the coffee. This results in a whipped-up the top of the espresso. This is one of the main characteristics of a good espresso.

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

The earliest espresso machines were steam types. The first espresso machines were steam types. This led to the coffee and espresso maker tasting burnt and bitter. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most well-known espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic espresso machine, you need to grind the beans and then tamp them by hand. However, the pump controls the flow of water and pressure. This is a great compromise between the human touch and mechanized quality.

The Filter

Typically, espresso machines have filters to separate the grounds of coffee as they move through the hot water. The filter is also an essential part of the temperature control system as it keeps the machine from overheating.

It also helps with flavor, as a filter lets you enjoy a longer bloom phase. This lets the beans release their nuances, and improves extraction.

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

This is where the magic happens, it's what makes espresso taste good. The grouphead, also called the brew head, is the place where the portafilter (the device you put the ground coffee in) is placed when making espresso.

Steam-driven espresso machines make use of hot water heated in an airtight container to produce steam. The steam then pushes hot water through grounds of the coffee under pressure. These machines are cheaper and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the perfect brewing conditions 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 make use of an air compressor to force hot water through the ground, and are more mobile than steam-driven electric espresso machines.