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How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. How exactly does it work?

Espresso is created by forcing hot water 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 that you insert when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the extraction. There are numerous kinds of group heads, each with its own advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. There are even some that come with a range of features, like the E61 that is the most popular choice among baristas due to its capacity to offer multiple perks in a single package.

As you can see in the above image The group head features many notches in which you can put your portafilter, then twist it with your hands to secure it. There is also a gasket made of rubber that is a part of the notches and helps create a seal when you insert your portafilter into the machine. The notches allow for an exact placement of the portafilter. This is essential for an efficient extraction.

The group head does not just allow you to put in your portafilter easily however it also keeps the temperature at a constant level. It does this by circulating hot water through the brew basket, and around the portafilter, ensuring that it is always at the right temperature to extract. It is important to realize that even a small deviation can make the difference between a decent and a great espresso.

The Pump

Unlike manual piston machines, which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to supply the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior it is shot through the ground coffee inside the group head.

Pumps are typically more affordable and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to excessive use and inadequate cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simpler models.

Some espresso machines do away with the pump entirely and employ steam pressure to create espresso. This can cause over-extraction because the boiler that makes steam also causes the water to boil. These machines espresso machines also have to constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines use a rotary or vibration pump. A vibration model makes use of an oscillating disk to create pressure, whereas the circular model pushes hot liquid through the ground at high speed. Both machines can make great espresso but rotary machines are more quiet, durable and less likely to break down.

The Boiler

The boiler is the component which heats the water to the optimal temperature to extract. The steam that is produced reaches the portafilter containing the ground espresso coffee and is then funneled down into the cup. In this process, the steam creates pressure and pushes through the grounds of the coffee. This results in a layer of crema that is then poured over. This is one of the main characteristics of a great espresso coffee machine home.

There are three types of espresso makers. They differ in the kind of pump they use and how hot the coffee is. There are various ways to control the strength of the brew and the size of the cup that can be made by the machine.

The first espresso machines were steam-type. They utilized a single boiler to make both steam and brew however the pressure they were able to generate was low - only two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most common espresso machine is a semiautomatic with an electric pump. These are the images people have when they imagine an espresso machine. With a semi-automatic espresso machine, you must grind the beans and tamp them by hand. The pump regulates the flow of water and pressure. This is an excellent compromise between human touch and the mechanised accuracy.

The Filter

Espresso machines usually use a filter that separates the grounds of the coffee from the hot water. The filter is also a vital part of the temperature control system, since it helps prevent the machine from overheating.

It also improves flavor, as it can allow for a longer bloom phase. This allows the beans to release their nuances and gives the chance for better extraction.

However, it is important to keep in mind that even a high-quality filter could result in a bad cup of coffee, as the quality of the beans and extraction is still crucial.

This is where the magic happens, it's what makes espresso taste great. The grouphead, sometimes referred to as the brew head, is the place where the portafilter (the thingy you put the coffee grounds into) sits when you're making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam. Steam is then pushed through the grounds with high pressure. These machines are cheaper and easier to maintain than pumps-driven models. However, they are not as efficient in their ability to create the perfect conditions for brewing, as they only operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.

In recent times, espresso machines powered by a compressed air compressor have become increasingly popular. They utilize an air compressor to force hot water through the grounds and are significantly more portable than steam-driven electric machines.