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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to make the coffee we love. But how exactly does it work?

In order 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 Group Head

The group head is the portafilter is inserted when you are making espresso. It is responsible for dispersing water into the portafilter and controlling the pressure that results from the extraction. There are numerous kinds of group heads each with its own advantages and drawbacks. Some are focused on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. There are some that have a combination of features, such as the E61 that is the standard choice for many baristas because of its ability to offer multiple perks in one package.

As you can see from the photo above, the group head is fitted with several notches. The portafilter is placed in these notches and then twist the head to lock it. A gasket made of rubber is positioned inside the notches to help create a seal while you insert your portafilter. The notches allow for an exact placement of the portafilter. This is vital for an accurate extraction.

In addition to allowing you easily connect your portafilter, the group head is also responsible to ensure that the temperature remains even. This is accomplished by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is at the right level for extraction. This is important because even a few degrees can make the difference between good and great espresso.

The Pump

In contrast to piston machines that are manually operated, which use a lever to pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure required to extract espresso. The pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger before being pumped through the ground coffee in the group head.

Pumps are typically cheaper and last longer than piston-driven machines. However, both kinds of machines can degrade due to excessive use and insufficient cleaning. Pumps are also more complex mechanically, which can increase the price of even the simpler models.

Some espresso machines remove the pump completely and instead employ steam pressure to create espresso. The drawback of this is that the same boiler that produces steam also increases the temperature of water until it reaches boiling which can cause excessive extraction. In addition these machines are often required to restore their pressure between cups, which takes time and energy.

Many espresso machines use a rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, while the Rotary model pushes hot coffee through the ground at a high speed. Both machines produce great espresso however rotary machines tend to be quieter, more durable and less likely to break.

The Boiler

The boiler is the one that will heat the water to the perfect temperature for extraction. The steam that is produced reaches the portafilter containing the ground espresso coffee and is then pumped into the cup. During this process, the steam creates pressure and pushes through the coffee grounds. This produces a layer of crema on top. This is one of the hallmarks of a good espresso.

There are three types of espresso makers. They differ in the kind of pump they use and the degree of heat that the brew is. There are a variety of ways in which the brew can 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 only one boiler to make both steam and brew however the pressure they were able to create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. This is the reason why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most popular espresso machine is a semiautomatic that has an electric pump. This is what people envision when they imagine an espresso machine. If you have a semi-automatic machine you grind the beans and then tamp them by hand. The pump controls the flow of water and pressure. This is an excellent compromise between human touch and mechanized accuracy.

The Filter

Espresso machines typically use filters that separate the grounds of the coffee from the hot water. The filter is also an important part of the temperature control system since it helps prevent the machine from overheating.

A filter also improves flavor since it allows for an extended flowering time. This lets the beans let their nuances out, machine espresso and allows for a better extraction.

It is important to remember that even the finest filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, are still crucial.

This is where the magic happens, it's the thing that makes espresso taste good. The grouphead (also known as the brewhead) is where you put the portafilter - the thingy that you use to put the grounds of coffee into when making espresso.

Steam-driven espresso machines use hot water heated in an airtight container to create steam. The steam then moves hot water through the grounds of coffee at high pressure. They are less expensive and are easier for the user to maintain than pumps-driven models. However, they are not as efficient in their ability to produce the perfect conditions for brewing, because they operate at 1-1.5 bars 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 the hot water through the grounds and are more portable than steam-driven electric machines.