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How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and incredible filter technology to produce the coffee we love. How does it work exactly?

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 primary difference.

The Head of the Group

As the name implies, the group head is where you place your portafilter when making espresso. It distributes water into the portafilter, and then regulates the pressure during the extraction. There are numerous kinds of group heads each with distinct advantages and drawbacks. Some focus on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. There are even some that contain a variety of features, like the E61, which is the standard choice for many baristas due to its ability to provide multiple benefits in a single package.

As you can see in the photo above the group head is made up of many notches in which you can place your portafilter before twisting it manually to secure it. A gasket of rubber is situated within the notches to create a seal while you insert your portafilter. The notches on the head permit a precise location of the portafilter which is essential to ensure a consistent extraction.

The group head is not just able to allow you to place your portafilter easily however it also keeps the temperature at a constant level. This is done by cycling hot water around the portafilter and through the brew-basket to ensure the temperature is always right for extraction. It is crucial to keep in mind that even a tiny difference can make the difference between a decent and a excellent espresso.

The Pump

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

Pumps are typically less expensive and last for longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to overuse and inadequate cleaning. Pumps are also more complicated mechanically, which can increase the cost of even most basic models.

Certain espresso machines can eliminate the pump completely and instead use steam pressure to brew Mini Espresso Machine. This can lead to over-extraction as the boiler that produces steam also warms the water to boil. In addition the machines often have to rebuild their pressure between cups, which requires time and energy.

A large majority of espresso machines employ an rotary or a vibration pump. A vibration model uses an oscillating disk to create pressure, while a circular model pushes hot liquid through the ground at a fast speed. Both models can produce an excellent espresso, but Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the component that heats water to the ideal temperature to extract. The resultant steam then reaches the portafilter, which contains the ground espresso and is then pumped into the cup. During this process the steam generates enough pressure to push the coffee grounds through. This results in a whipped-up top of the espresso. This is the hallmark of a great espresso.

There are three kinds of espresso machines, each with different pumps and the temperature of the brew. There are various ways to control the strength of the brew and the size of the cup that can be produced by the machine.

The first espresso machines were steam-type. They employed a single boiler to make both brew and steam, however the pressure they were able to create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most popular espresso machine is a semiautomatic one with an electric pump. These are the things people think of when they think of an espresso machine. With a semi-automatic machine, you grind the beans and then tamp them by hand. However, the pump is able to regulate the flow of water and pressure. This is a great compromise between the human touch and mechanized consistency.

The Filter

Espresso machines typically have filters that separate the grounds of coffee from hot water. The filter is also an essential component of the machine's temperature control, as it prevents overheating.

A filter also helps with flavor because it allows for an extended flowering time. This helps the beans release their flavors and provides an opportunity for better 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 process, are still crucial.

This is where the magic happens, and it's what makes espresso taste great. The grouphead, often called the brewhead, is where the portafilter (the thing you put the coffee grounds into) is placed when making espresso.

Steam-driven espresso machines make use of hot water heated in an airtight container to make steam. The steam then moves hot water through the grounds of coffee under high pressure. These kinds of machines are usually cheaper and easier to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water into the ground. They are also more mobile than electric steam-driven barista espresso machine machines.