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How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and mind-blowing filter technology to make 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. However, the pressure is the major difference.

The Head of the Group

As the name suggests the group head is where you place your portafilter when making espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure that results from the extraction. There are many different types of group heads, each with its own advantages and disadvantages. Some are designed to provide the stability of temperature while some are specifically designed to handle pre-infusion. Others are made to control the lever. There are even some that come with a range of features, such as the E61 that 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 above photo the group head comes with several notches where you place your portafilter before twisting it with your hands to lock it in. A gasket of rubber is situated inside the notches, which helps create a seal while you insert your portafilter. The notches allow for precise placement of the portafilter. This is crucial to ensure an even extraction.

The group head does not just allow the portafilter to be inserted easily however it also keeps an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is constant for extraction. This is crucial, since even a few degrees can make the difference between good and great espresso.

The Pump

Unlike manual piston machines, which rely on a lever that pressurize water, the rotary espresso coffee makers machines use motorized pumps that provide the nine atmospheric bars of pressure that are required to extract espresso. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger before being shot through the ground coffee in the group head.

Pumps tend to be less expensive than piston-driven machines, and they tend to last longer, however both types of machine can get damaged through overuse and lack of cleaning. They also create mechanical complexity, which can result in a high price tag on even the most basic models.

Some espresso machines remove the pump completely and instead utilize steam pressure to make espresso coffee maker. This could lead to over-extraction since the boiler that makes steam also warms the water to boil. In addition the machines often have to restore their pressure between cups, which takes time and energy.

A majority of espresso machines utilize either a vibration or rotary pump. A vibration model makes use of an oscillating disk to create pressure, while a rotary model pushes hot water through the ground at a rapid speed. Both machines produce great espresso however rotary machines tend to be quieter, more durable and less likely to fail.

The Boiler

The boiler is used to heat the water to the perfect temperature for extraction. The steam that is produced reaches the portafilter that contains the ground espresso coffee, and gets funnelled down into the cup. The steam causes enough pressure to push the coffee grounds through. This creates a foam on top of the espresso. This is one of the hallmarks of a good espresso.

There are three kinds of espresso machines, each having different pumps and the temperature of the brew. There are various ways in which the brew could be controlled, as well as the dimensions of the cup the machine can produce.

The first espresso machines were steam-types. The earliest professional espresso machine for home machines were steam types. The coffee tasted bitter and burned. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most well-known espresso maker is a semiautomatic machine that has an electric pump. These are the things people think of when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp your beans yourself while the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized quality.

The Filter

Espresso machines usually use a filter that separates the grounds of coffee from hot water. The filter is also a crucial part of the temperature control system as it prevents the machine from overheating.

It also enhances flavor, as a filter allows for a longer bloom time. This helps the beans to release their nuances and gives the chance for better extraction.

However it is crucial to keep in mind that even a top filter can result in a poor cup of coffee, as the quality of the beans and extraction are crucial.

This is where the magic happens. It's what makes an espresso really taste good. The grouphead (also known as the brewhead) is where you place the portafilter - the thingy that you put the coffee grounds in, while making espresso.

Steam-driven espresso machines use hot water that is heated in an airtight container to produce steam. The steam then pushes hot water into the grounds of the coffee under pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. However, they are limited in their ability to provide the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.

In recent years, compressed-air-pump-driven espresso machines have become more popular. They use an air-compressor to force hot water through the ground and are much more mobile than electric steam-driven professional espresso maker machines.