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How Does Machine Espresso Work?

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

Espresso is created by forcing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee. However it is the pressure that makes the main difference.

The Group Head

As the name suggests the group head is where you place your portafilter when brewing espresso. It disperses water in the portafilter, and regulates the pressure of extraction. There are many different types of group heads, each with its own advantages and disadvantages. Some are focused on temperature stability, others on pre-infusion features, and others are designed to control the lever. Some have a combination of features, like the E61, which is considered the standard choice for many baristas due to its capacity to offer multiple perks in one package.

As you can see from the image above, the group head is fitted with several notches. The portafilter is placed inside these notches, and then turn the head around to secure it. A gasket made of rubber is positioned inside the notches, which helps make a seal when you insert your portafilter. The notches on the head allow for an exact placement of the portafilter, which is essential to ensure an even extraction.

In addition to allowing you to easily insert your portafilter, the group head is responsible to maintain an even temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket to ensure the temperature is always right to extract the coffee. It is important to remember that even a few degree differences can make the distinction between a great and a excellent espresso.

The Pump

The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure that is required to extract espresso. This is different from manual piston machines that use a lever. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are typically less expensive than piston-driven models, and they tend bean to cup espresso machine last longer, however both types of machines could become damaged due to excessive use and poor cleaning. They also add mechanical complexity which can result in an expensive price for even the most basic models.

Certain espresso machines can eliminate the pump completely and employ steam pressure to create espresso machine coffee. The disadvantage of this is that the boiler that produces steam also raises the temperature of the water to boiling which can cause over-extraction. In addition these machines are often required to restore their pressure between cups, which takes time and energy.

Many espresso machines employ the rotary or vibration pump, with a vibrating model using a vibrating disc that generates the pressure and rotating models that push hot water through the grounds at high speed. Both machines can make great espresso however rotary machines tend to be more stable, quieter and less likely to break.

The Boiler

The boiler is the one that is used to heat the water to the right temperature for extraction. The steam that is produced reaches the portafilter, which contains the ground espresso coffee and is then funneled down into the cup. During this process the steam is able to create enough pressure to push the grounds of coffee through. This creates a crema on top of the espresso. This is one of the main characteristics of a great espresso.

There are three kinds of espresso machines, each with different types of pumps and the temperature of the brew. There are also different ways that the brew may be controlled as well as the size of the cup that the machine can produce.

The first espresso machines were steam-based. They employed a single boiler to make both steam and brew but the pressure they could create was minimal - two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. This is why the Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most common 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 machine you grind the beans and tamp them by hand. The pump regulates the flow of water and pressure. This is an excellent combination of human control and mechanized reliability.

The Filter

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

A filter also helps with flavor, as it permits a longer flowering period. This lets the beans release their flavors, and allows for a better extraction.

However, it is important to remember that even a high-quality filter can make a terrible cup of coffee as the quality of the beans and extraction is still essential.

It's here that the magic occurs. This is what makes espresso taste so delicious. The grouphead (also known as the brewhead) is where you place the portafilter - the thingy that you use to put the grounds of coffee into while making espresso.

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 types of machines are generally less expensive and easier to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9 bar espresso machine-10 bar.

In recent years, decent espresso machine machines powered by a compressed air pump have become increasingly popular. They utilize an air compressor to push hot water through the ground and are more mobile than electric steam-driven espresso machines.