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How Does Machine espresso coffee machines Work?

Machine espresso employs precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly does it work?

Espresso is created by forcing hot water under pressure through finely ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure.

The Head of the Group

As the name suggests the group head is where you put your portafilter in when brewing espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure that results from the extraction. There are many different types of group heads each with its own advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. There are also some that come with a range of features, such as the E61 that is to be the most popular among baristas for its ability to offer multiple perks in a single package.

As you can see in the image above the group head comes with several notches where you put your portafilter, then twist it by hand to lock it in. A rubber gasket is located inside the notches to help make a seal when you insert your portafilter. The notches allow for the precise placement of the portafilter. This is essential for an even extraction.

Aside from allowing you to easily place your portafilter in, the group head is responsible to maintain an even temperature. This is done by cycling hot water around the portafilter and through the brew basin, ensuring the temperature is always right to extract the coffee. This is important, as just a few degrees could be the difference between a excellent and great espresso.

The Pump

The motorized pumps used in espresso machines rotary provide nine atmospheric bars of pressure required to extract espresso. This is different from manual piston machines that rely on levers. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger prior it is shot 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 are susceptible to degrading due to overuse and insufficient cleaning. Pumps are also more complicated mechanically, which can increase prices of even simple models.

Some espresso machines remove the pump completely and employ steam pressure to create espresso. This can lead to over-extraction as the boiler that makes steam also heats the water to boil. Additionally these machines typically have to restore their pressure between cups, which requires time and energy.

Many espresso machines make use of the rotary or vibration pump, which is a vibration model using a rotating disc to create the pressure, and the rotary model pushing hot water through the grounds under high speed. Both types of machines can produce an excellent espresso, but the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is the element that heats water to an optimal temperature to extract. The resulting steam is then transferred to the portafilter that contains the ground espresso and is then pumped into the cup. The steam generates enough pressure to push the coffee grounds through. This results in a layer crema on top. This is one of the hallmarks of a great espresso.

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

The first espresso machines were steam-types. They utilized one boiler to create both steam and brew however the pressure they were able to produce was very low - just two bars of atmospheric pressure at the most. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso maker is a semi-automatic one with an electric pump. These are the images people have when they think of an espresso machine. With a semi-automatic espresso machine, you grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanized consistency.

The Filter

Espresso machines typically have a filter that separates the grounds of the coffee from hot water. The filter is also a vital element of the machine's temperature control, since it helps to prevent overheating.

A filter also improves flavor, as it permits an extended flowering time. This allows beans to release their nuances and gives the chance for better extraction.

It is important to remember that even the most efficient filter can result in a bad cup of coffee. The quality of the beans and the extraction process, remain crucial.

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

In a steam-driven espresso machine hot water is heated in an airtight container to produce steam, which is then pushed through the grounds under high 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 ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The ideal 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 into the ground, and are more mobile than steam-driven electric espresso machines.