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How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and incredible filter technology to produce the delicious coffee we enjoy. What exactly is it?

Espresso is produced by pushing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure.

The Head of the Group

The name implies, the group head is where you put your portafilter in when brewing espresso. It disperses water in the portafilter, and then regulates the pressure of extraction. There are a variety of types of group head, each with their particular advantages and disadvantages. Some are designed to provide stability of temperature while others are built to handle pre-infusion. Others are built to control the lever. Some have a combination, like the E61. This is a very popular choice for baristas due to the fact that it has multiple advantages in a single package.

As you can see in the image above the head of the group is fitted with a variety of notches. You place your portafilter inside these notches, and then turn the head around to secure it. A gasket made of rubber is placed inside the notches to help create a seal while you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is crucial for an efficient extraction.

The group head not only allows you to insert your portafilter easily however it also keeps a constant temperature. It does this by circulating hot water through the brew basket, and around the portafilter to ensure that it's always at the correct temperature to extract. This is crucial, since even a few degrees can mean the difference between excellent and great espresso.

The Pump

Unlike manual piston machines, which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure necessary for espresso extraction. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.

Pumps are generally cheaper and last longer than piston-driven machines. However, both kinds of machines can deteriorate due to overuse and poor cleaning. Pumps are also more complicated mechanically, which can increase prices of even simplest models.

Certain espresso machines remove the pump completely and instead utilize steam pressure to make espresso. This can cause over-extraction because the boiler that makes steam also warms the water to boil. They also have bean to cup espresso machine continuously rebuild their pressure between cups. This requires 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 Rotary model pushes hot coffee through the ground at a high speed. Both machines can produce excellent espresso but rotary machines are more stable, quieter and less likely to break down.

The Boiler

The boiler is the one that heats the water to the ideal temperature to extract. The resulting steam is then transferred to the portafilter that contains the ground espresso coffee and is then pumped down into the cup. The steam generates enough pressure to push the grounds of the coffee through. This results in a crema on top of the espresso. This is a hallmark of a good espresso.

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

The first espresso machine with milk frother machines were steam-types. The first espresso machines were steam types. This led to the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic espresso machine, you have to grind the beans and then tamp them by hand, but the pump is able to regulate the flow of water and pressure. This is an excellent compromise between human touch and the mechanised accuracy.

The Filter

Typically, espresso machines have filters that separate the grounds of coffee as they move through the hot water. The filter is also a vital part of the machine's temperature control, since it helps to prevent overheating.

It also enhances flavor, since a filter allows for a longer bloom time. This helps the beans release their flavor and gives an opportunity for a better extraction.

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

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

In a steam-driven espresso machine, hot water is heated in an airtight tank to produce steam, which then pushes the hot water through the grounds under high pressure. They are less expensive and easier for the user to maintain than pumps-driven models. However, they are limited in their capacity to create the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.

In recent years, compressed air-driven espresso machines have been gaining popularity. They use an air compressor to force hot water into the ground and are more mobile than electric steam-driven espresso machine coffee machines.