How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and incredible filter technology to produce 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. However the pressure is the main difference.

The Group Head

The group head is the portafilter you place in the espresso maker when making it. It disperses water in the portafilter, and then regulates the pressure during the extraction. There are various kinds of group head each with its unique advantages and drawbacks. Some focus on temperature stability, while others on pre-infusion options, and others are designed to control the lever. There are some that come with a range of features, such as the E61 one, which is the most popular choice among baristas due to its capacity to offer multiple perks in a single package.

As you can see in the image above the head of the group is fitted with several notches. You place your portafilter inside these notches, and then twist the head to secure it. There is also a gasket of rubber that is a part of the notches, which helps create a seal when you insert your portafilter into the machine. The notches on the head allow for an exact placement of the portafilter, which is vital to ensure a consistent extraction.

Aside from allowing you to effortlessly insert your portafilter the group head is also responsible to ensure that the temperature remains even. It does this by circulating hot water through the brew basket and around the portafilter, ensuring that it's always at the correct temperature to extract. This is crucial, since even a few degrees can mean the difference between good and excellent espresso.

The Pump

The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure that is required for espresso extraction. This is different from manually operated piston machines that employ a lever. The pressure builds up by removing tap water from a reservoir and pumping it through a heat exchanger prior being pumped through the ground coffee in the group head.

Pumps are typically more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and inadequate cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simplest models.

Some espresso machines use steam pressure instead of a pump to make espresso. This can lead to over-extraction as the boiler that makes steam also warms the water to boil. Additionally the machines often have to rebuild their pressure between cups, which requires time and energy.

Many espresso machines use an rotary or a vibration pump. A vibration model utilizes a vibrating disk to generate pressure, while a rotating model pushes hot water through the ground at a high speed. Both machines can make great espresso, but rotary machines are quieter, more durable and less likely to fail.

The Boiler

The boiler is the component that heats water to the ideal temperature to extract. The steam that is created reaches the portafilter, which is a container for espresso grounds. It is then pumped into the cup. During this process, steam creates pressure and pushes through the grounds of the coffee. This produces a layer of crema on top. This is one of the hallmarks 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 different ways in which the brew can be controlled and the dimensions of the cup the machine can produce.

The first espresso machines were steam type. They utilized only one boiler to make both steam and brew, however, the pressure they could create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic machine you must grind the beans and tamp them by hand. However, the pump regulates the flow of water and pressure. This is an excellent compromise between human touch and the mechanised accuracy.

The Filter

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

It also improves flavor as a filter allows for a more prolonged bloom phase. This helps the beans to release their flavors and provides the chance for better extraction.

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

This is where the magic happens, and it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you put the portafilter - the thingy which you put the grounds of coffee into when making retro espresso machine.

In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam, which is then pushed through the grounds under high pressure. These kinds of machines are typically less expensive and simpler to maintain than pump-driven models. They are however limited to create the perfect conditions for brewing, as they 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 through the ground. They are also more mobile than electric steam-driven espresso machines.