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How Does Machine Espresso Work?

The machine espresso makes use of precise pressure and filter technology that is mind-blowing to create the coffee you love. But how exactly does it work?

To make an espresso machine coffee hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure.

The Head of the Group

The group head is the portafilter that you put in when making espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the extraction. There are a variety of types of group heads each with its own advantages and drawbacks. Some are designed to provide the stability of temperature while some are built to handle pre-infusion. Some are designed to control the lever. Some come with a range of features, such as the E61 one, which is to be the most popular among baristas because of its ability to offer multiple perks in one package.

As you can see in the above photo the group head is made up of several notches to put your portafilter, then twist it manually to secure it. A rubber gasket is located in the notches to make a seal when you insert your portafilter. The notches on the head allow for an exact placement of the portafilter, which is essential for an efficient extraction.

Aside from allowing you to effortlessly insert your portafilter the group head is responsible for maintaining a consistent temperature. It does this by cycling hot water through the brew basket, and around the portafilter, making sure that it's always at the right temperature for extraction. It is important to note that even a tiny differences can make the distinction between a decent and a great espresso.

The Pump

The motorized pumps that are used in espresso machines that rotate provide the nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines that rely on levers. The pressure is created by drawing 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 cheaper and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and inadequate cleaning. Pumps are also more complex mechanically, which can raise the cost of even most basic models.

Certain espresso machines do away with the pump entirely and use steam pressure to brew espresso. The downside is that the same boiler that produces steam also raises the temperature of water until it reaches boiling, which can lead to over-extraction. The machines also need to constantly rebuild their pressure between cups. This takes energy and time.

A large majority of espresso machines employ either a vibration or rotary pump. A vibration model employs a vibrating disk to generate pressure, while a circular model pushes hot liquid through the ground at a rapid speed. Both types of machine can make a great espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is what will heat the water to a temperature that is ideal for extraction. The steam produced gets to the portafilter which holds the espresso grounds. It is then pumped into the cup. During this process, steam creates pressure that pushes through the coffee grounds. This creates a layer crema on top. This is a sign of a great espresso.

There are three kinds of espresso makers, and they differ in the kind of pump they use and the degree of heat that the brew is. There are different ways to control the brew and the size of cup that can be produced by the machine.

The first espresso machines were steam-type. They utilized only one boiler to make both brew and steam, however the pressure they were able to produce was not very high - two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most popular espresso machine is a semiautomatic that has an electric pump. These are the things people think of when they imagine an espresso machine. With a semi-automatic machine, you grind the beans and then tamp them by hand. The pump provides regulated water flow and pressure. This is an excellent compromise between human touch and the mechanized quality.

The Filter

Typically, espresso machines employ filters that separate the grounds of coffee when they pass through the hot water. The filter is also an essential element of the machine's temperature control, since it stops overheating.

It also helps with flavor as a filter allows for a more prolonged bloom phase. This allows the beans to release their nuances, and allows for a better extraction.

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

This is where the magic happens, and it's what makes an espresso really taste good. The grouphead (also called the brewhead) is where you put the portafilter, which is the thingy which you put the coffee grounds in, while making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam. This is then pushed through the grounds at a high pressure. These types of machines are typically cheaper and easier to maintain than pumps-driven models. However, they are limited in their ability to produce the ideal conditions for brewing because they operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.

In recent years, compressed-air-pump-driven espresso machines have become more popular. They utilize an air compressor to push hot water into the grounds and are much more portable than electric steam-driven machines.