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How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to create the coffee we love. What exactly is it that makes it work?

Espresso is made by pushing hot water under pressure through finely ground coffee. The process is similar to making drip coffee machine espresso but the difference is in the pressure.

The Group Head

As the name suggests the group head is the place you place your portafilter when making espresso. It disperses water into the portafilter, and regulates the pressure of extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. Some include a combination like the E61. This is a preferred choice for baristas due to the fact that it has multiple advantages in a single package.

As you can see from the image above the head of the group is fitted with several notches. It is possible to place your portafilter in these notches, then twist the head to secure it. There is also a gasket made from rubber which is located inside the notches and helps to create a seal when you insert your portafilter into the machine. The notches permit an exact placement of the portafilter. This is crucial for an efficient extraction.

The group head not only lets the portafilter to be inserted easily however, it also keeps a constant temperature. It does this by circulating hot water through the brew container and around the portafilter, ensuring that it's always at the correct temperature for extraction. This is crucial, since even a small difference in temperature can mean the difference between excellent and great espresso.

The Pump

The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure needed for espresso extraction. This is different from manual piston machines that use a lever. The pressure is created by removing tap water from a reservoir and pumping it through a heat exchanger prior to being pushed through the ground coffee inside the group head.

Pumps are typically less expensive and last longer than piston-driven machines. However, both types of machines may degrade because of excessive use and poor cleaning. They also add mechanical complexity which can result in a high price tag on even the simplest models.

Certain espresso machines utilize steam pressure instead of a pump for brewing espresso. This can lead to over-extraction as the boiler that produces steam also warms the water to boil. In addition these machines are often required to restore their pressure between cups, which takes time and energy.

Many espresso machines use an rotary or a vibration pump. A vibration model uses a rotating disk to generate pressure, whereas a rotary model pushes hot water through the ground at a fast speed. Both machines can produce excellent espresso, however rotary machines are more quiet, durable and less likely to fail.

The Boiler

The boiler is the one that heats the water to the ideal temperature to extract. The steam that is produced will eventually reach the portafilter, which contains the espresso coffee grounds. It is then pumped into the cup. The steam generates enough pressure to push the grounds of coffee through. This creates a layer crema that is then poured over. This is a sign of a great espresso.

There are three distinct types of espresso machines, each with different types of pumps and the temperature of the brew. There are different ways in which the brew could be controlled, as well as the dimensions of the cup the machine can make.

The earliest espresso machines were steam-based. They utilized one boiler to make both steam and brew but the pressure they could generate was low - only two bars of atmospheric pressure, at most. This resulted in the coffee for espresso machine tasting bitter and burnt. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most popular buy espresso makers machine is a semiautomatic with an electric pump. These are the things people think of when they think of an espresso maker. With a semi-automatic machine you grind the beans and then tamp them by hand, but the pump regulates the flow of water and pressure. This is a great solution that combines human control with mechanised accuracy.

The Filter

Typically, espresso machines employ filters to separate the grounds of coffee as they move through the hot water. The filter is also a vital element of the temperature control system, because it stops the machine from overheating.

It also improves flavor, as it can allow for a longer bloom phase. This allows the beans to let their nuances out and provides an opportunity to improve extraction.

It is important to keep in mind that even the best filter can produce a bad cup of coffee. The quality of the beans, as well as the extraction, remain crucial.

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

In a steam-driven espresso machine hot water is heated in an airtight container to create steam, which then pushes the hot water through the grounds with high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the perfect conditions for brewing, because they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar.

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