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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it?

To make an espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the main difference.

The Group Head

The group head is the portafilter that you put in when making espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the resulting extraction. There are various kinds of group head each with its distinct advantages and drawbacks. Some focus on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some come with a range of features, like the E61, which is considered the classic choice among many baristas because of its ability to provide multiple benefits in a single package.

As you can see in the picture above the group head is fitted with several notches. The portafilter is placed in these notches and then twist the head to secure it. There is also a rubber gasket that is a part of the notches to help create a seal when you insert your portafilter into the machine. The notches on the head permit an exact position of the portafilter which is essential for a consistent extraction.

Aside from allowing you to effortlessly insert your portafilter the group head is responsible for maintaining an even temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket, ensuring the temperature is always right for extraction. This is crucial, since even a small difference in temperature can mean the difference between good and excellent espresso.

The Pump

In contrast to manual piston machines that use a lever to pressurize water, machine espresso rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure needed for espresso extraction. The pressure is created by removing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.

Pumps are typically less expensive than piston-driven models, and they tend to last longer, although both types of machines can be damaged by excessive use and inadequate cleaning. Pumps are also more complicated mechanically, which can increase the price of even the simpler models.

Some espresso machines can eliminate the pump completely and utilize steam pressure to make espresso. The drawback of this is that the boiler that produces steam also increases the temperature of the water until it reaches boiling and can result in over-extraction. In addition these machines are often required to rebuild their pressure between cups, which takes time and energy.

Many espresso machines use the rotary or vibration pump. A vibration model uses a rotating disk to generate pressure, while a rotary model pushes hot water through the ground at a fast speed. Both machines can make great espresso however rotary machines tend to be quieter, more durable and less likely to break down.

The Boiler

The boiler is the part which heats the water to the ideal temperature to extract. The steam that is produced reaches the portafilter, which is the container that holds the espresso coffee grounds. It is then poured into the cup. The steam creates pressure and pushes through the coffee grounds. This creates a foam on the top of the espresso. This is the hallmark of a great espresso.

There are three types of espresso makers, which 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 cup that can be made by the machine.

The earliest espresso machines were steam-based. They utilized a single boiler to make both brew and steam, however, the pressure they could create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. The modern espresso machine was created by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso maker is a semiautomatic machine with an electric pump. When people think of espresso machines, they picture these machines. With 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 a great compromise between the human touch and the mechanised accuracy.

The Filter

Espresso machines typically have a filter that separates the grounds of the coffee from the hot water. The filter is also an important element of the temperature control system as it prevents the machine from overheating.

Filters also aid in flavor because it allows for a longer flowering period. This lets the beans release their flavors, and improves extraction.

However, it is important to remember that even a great filter can result in a poor cup of coffee, since the quality of the beans and extraction is still essential.

This is where the magic happens, and it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you place the portafilter, the thingy that you put the grounds of coffee into when making espresso.

Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water into the grounds of coffee at high pressure. They are less expensive and easier for the owner to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the ideal conditions for brewing since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars.

In recent years, compressed air-pump-driven best budget espresso machine machines have been gaining popularity. They utilize an air compressor to force the hot water through the grounds and are much more portable than steam-driven electric machines.