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How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly does it work?

To make an espresso hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However, the pressure is the primary difference.

The Head of the Group

As the name suggests, the group head is the place you insert your portafilter when making espresso. It distributes water into the portafilter, and then regulates the pressure of the extraction. There are several different types of group heads, each with their distinct advantages and drawbacks. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Others are made to control the lever. Some are a combination, like the E61. This is a preferred choice for baristas due to the fact that it has multiple advantages in one package.

As you can see from the image above the head of the group is fitted with several notches. You place your portafilter into these notches and turn the head around to secure it. A rubber gasket is located inside the notches to help create a seal as you insert your portafilter. The notches allow for the precise placement of the portafilter. This is crucial to ensure an efficient extraction.

Apart from allowing you easily insert your portafilter, the group head is responsible to ensure that the temperature remains even. This is accomplished by cycling hot water around the portafilter and through the brew-basket, ensuring that the temperature is constant for extraction. It is important to realize that even a tiny variation can mean the difference between a good and excellent espresso.

The Pump

Contrary to manual piston machines which rely on a lever that pressurize water, rotary compact espresso machine machines rely on motorized pumps to deliver the nine atmospheric bars of pressure needed to extract espresso. The pressure is created by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pushed through the ground coffee and espresso maker in the group head.

Pumps are typically more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and insufficient cleaning. Pumps are also more complicated mechanically, which can increase prices of even simple models.

Certain espresso machines utilize steam pressure instead of a pump to make espresso. The drawback of this is that the same boiler that produces steam also raises the temperature of the water until it reaches boiling, which can lead to excessive extraction. The machines also need to constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines make use of a rotary or vibration pump. A vibration model uses a vibrating disk to generate pressure, whereas the Rotary model pushes hot coffee through the ground at a high speed. Both machines can make excellent espresso however rotary machines tend to be more stable, quieter and less likely to fail.

The Boiler

The boiler is the one that makes the water warm to a temperature that is ideal for extraction. The steam that is created reaches the portafilter, which contains the espresso coffee grounds. It is then funneled into the cup. During this process, the steam causes pressure to push through the grounds of the coffee. This results in a layer of crema on top. This is one of the main characteristics of a good retro espresso maker.

There are three kinds of espresso makers, which differ in the type of pump they use and how hot the barista espresso coffee machine is. There are different ways to control the amount of brew, as well as the size of cup that can be made by the machine.

The first espresso machines were steam-type. They employed one boiler to create both brew and steam, however, the pressure they could produce was very low - just two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso maker is a semiautomatic machine with an electric pump. When people think of espresso machines, they envision these machines. If you have a semi-automatic machine you must grind the beans and 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 quality.

The Filter

Typically, espresso machines use a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a vital component of the machine's temperature control, as it prevents overheating.

A filter also helps with flavor since it allows for a longer flowering period. This allows the beans to release their nuances and gives the chance for better extraction.

It is important to keep in mind that even the best filter could result in a poor cup of coffee. The quality of the beans and the extraction, remain crucial.

It's here that the magic happens. This is what makes espresso taste so delicious. The grouphead (also called the brewhead) is where you put the portafilter - the thingy used to place the coffee grounds in, when making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then pushes hot water into the grounds of the coffee under pressure. These types of machines tend to be less expensive and easier to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They use an air compressor to push hot water through the ground. They are also more mobile than electric steam-driven espresso machines.