Maisie Birdwood

How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to make the perfect cup of coffee. What exactly does it work?

Espresso is made by forcing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee. However the pressure is the primary difference.

The Group Head

The group head is the portafilter you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are numerous kinds of group heads each with their own advantages and drawbacks. Some focus on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. There are some that come with a range of features, such as the E61, which is the most popular choice among baristas because of its ability to offer multiple benefits in one package.

As you can see in the image above, the group head has several notches to put your portafilter, then twist it manually to lock it in. There is also a gasket of rubber in the notches and helps to create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact location of the portafilter which is essential to ensure an even extraction.

In addition to 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 basket and around the portafilter, making sure that it's always at the right temperature to extract. It is important to realize that even a tiny differences can make the distinction between a decent and a great espresso.

The Pump

The motorized pumps used in espresso machines that rotate provide the nine atmospheric bar pressure that is required for espresso extraction. This is different from manual piston machines that rely on a lever. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be cheaper than piston-driven machines, and they tend to last longer, however both types of machine can degrade with overuse and insufficient cleaning. Pumps are also more complicated mechanically, which could increase the cost of even simplest models.

Some espresso machines remove the pump entirely and make use of steam pressure to make espresso. This can cause over-extraction because the boiler that makes steam also causes the water to boil. Additionally these machines typically have to restore their pressure between cups, which requires time and energy.

Many espresso machines utilize either a rotary or vibration pump, with a vibration model using a vibrating disc to create pressure and an rotary model that pushes hot water through the grounds under high speed. Both machines can produce excellent espresso, however rotary machines are more quiet, durable and less likely to break down.

The Boiler

The boiler is what makes the water warm to the ideal temperature to extract. The resultant steam then reaches the portafilter that contains the ground espresso coffee, and is then funneled down into the cup. In this process, the steam creates pressure and pushes through the coffee grounds. This creates a layer crema on top. This is a sign of a great espresso.

There are three kinds of espresso makers, and they differ in the type of pump they use and the degree of heat that the brew is. There are a variety of ways that the brew can be controlled, as well as the dimensions of the cup the machine can make.

The earliest espresso machines were steam-based. They had one boiler to create steam and brew, however the pressure they were able to generate was low - only two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso machine is a semiautomatic that has an electric espresso maker 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 then tamp them by hand. The pump is able to regulate the flow of water and pressure. This is a great compromise between the human touch and the mechanized consistency.

The Filter

Typically, espresso machines use filters that separate the grounds of coffee when they pass through the hot water. The filter is also an important component of the temperature control system as it keeps the machine from overheating.

A filter also helps with flavor since it allows for an extended flowering time. This allows the beans to release their flavors, and allows for better extraction.

It is important bean to cup espresso machines keep in mind that even the finest filter can make a bad cup of coffee. The quality of the beans and the extraction process, remain vital.

This is where the magic happens, it's the thing that makes an espresso really taste great. The grouphead, sometimes referred to as the brewhead, is where the portafilter (the container you place the coffee ground into) is placed when making espresso.

In the steam-driven espresso machine hot water is heated in an airtight tank to produce steam, which is then pushed through the grounds at high pressure. These kinds of machines are generally less expensive and easier to maintain than pump-driven models. However, they are limited in their ability to create the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.

In recent years, compressed air-driven espresso machines have become more popular. They use an air compressor to push hot water through grounds and are more portable than electric steam-driven machines.