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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and amazing filter technology to make the coffee we love. What exactly is it?

To make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, however the main difference lies in the pressure.

The Head of the Group

The group head is the portafilter that is inserted when you are making espresso. It distributes water into the portafilter, and then controls the pressure of the extraction. There are a variety of types of group head each with its particular advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. Some come with a range of features, like the E61 one, which is the classic choice among many baristas due to its capacity to offer multiple perks in a single package.

As you can see in the above image the group head comes with many notches in which you can place your portafilter before twisting it with your hands to lock it in. A gasket made of rubber is placed inside the notches to help create a seal while you insert your portafilter. The notches allow for the precise placement of the portafilter. This is crucial for an even extraction.

The group head not only allows you to insert your portafilter easily however it also keeps the temperature at a constant level. It does this by cycling hot water through the brew basket, and around the portafilter, ensuring that it's always at the correct temperature to extract. This is vital, because even a small difference in temperature can make the difference between a good and great espresso.

The Pump

Unlike manual piston machines, which rely on a lever that pressurize water, rotary espresso coffee machine uk machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally cheaper and last longer than piston-driven machines. However, both kinds of machines can degrade because of excessive use and insufficient cleaning. They also create mechanical complexity, which can result in costly prices for even the most basic models.

Some espresso machines do away with the pump completely and instead use steam pressure to brew espresso. This can lead to over-extraction as the boiler that produces steam also heats the water to boil. Additionally these machines typically have to restore their pressure between cups, which requires time and energy.

A large majority of espresso machines employ either a vibration or rotary pump. A vibration model uses a rotating disk to generate pressure, while a circular model pushes hot liquid through the ground at a high speed. Both types of machines can make excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the part that heats water to an optimal temperature to extract. The resulting steam is then transferred to the portafilter which holds ground espresso beans and is then pumped down into the cup. The steam creates pressure that pushes through the coffee grounds. This results in a layer crema on top. This is a sign of a good barista espresso coffee machine.

There are three different types of espresso machines, each with different types of pumps and the temperature of the brew. There are different ways that the brew may be controlled as well as the size of the cup the machine is capable of making.

The first espresso machines were steam-types. They utilized one boiler to create both steam and brew but 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 created by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso machine is a semiautomatic model with an electric pump. This is what people envision when they think of an espresso maker. If you have a semi-automatic machine you must grind the beans and then tamp them by hand. However, the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanised quality.

The Filter

Typically, espresso machines have filters to separate the coffee grounds as they pass through the hot water. The filter is also an essential element of the machine's temperature control, since it helps to prevent overheating.

It also aids in flavor, since a filter lets you enjoy a longer bloom phase. This allows the beans to release their flavors and provides the chance for better extraction.

It is important to keep in mind that even the most efficient filter could result in a poor cup of coffee. The quality of the beans and the extraction, are still very important.

This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead, often referred to as the brew head, is the place where the portafilter (the thing you put the ground coffee into) is located when you're making decent espresso machine.

Steam-driven espresso machines use hot water heated in an airtight container to make steam. The steam then pushes hot water into the grounds of coffee under high pressure. These machines are less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to provide the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.

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