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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to make the perfect cup of coffee. But how exactly does it work?

In order to make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to that of making drip coffee. However, the pressure is the major difference.

The Group Head

The name implies, the group head is where you place your portafilter while making espresso. It distributes water into the portafilter and regulates the pressure of the extraction. There are numerous kinds of group heads each with its own advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. There are also some that contain a variety of features, like the E61, which is considered the standard choice for many baristas due to its ability to offer multiple benefits in one package.

As you can see in the image above the head of the group is equipped with several notches. The portafilter is placed in these notches, then twist the head to lock it. There is also a rubber gasket that resides inside the notches and helps create an airtight seal after inserting your portafilter into the machine. The notches allow for precise placement of your portafilter. This is essential for an even extraction.

Apart from allowing you effortlessly insert your portafilter the group head is also responsible to ensure that the temperature remains even. This is accomplished by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is always at the right level to extract the coffee. This is important because just a few degrees could make the difference between a good and great espresso.

The Pump

The motorized pumps in rotary espresso machines supply the nine atmospheric bar pressure needed for espresso extraction. This is different from manual piston machines which use levers. The pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being pumped through the best ground coffee for espresso machine coffee inside the group head.

Pumps are typically less expensive than piston-driven models, and they tend to last longer, however both types of machines can get damaged through overuse and lack of cleaning. Pumps are also more complex mechanically, and can add to the price of even the simple models.

Some espresso machines use steam pressure instead of a pump bean to cup espresso machines brew espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of the water until it reaches boiling, which can lead to over-extraction. Additionally the machines often have to rebuild their pressure between cups, which takes time and energy.

A majority of espresso machines use the rotary or vibration pump, with a vibration model that uses a vibrating disc to create the pressure, and a rotary model pushing hot water through the grounds at high speed. Both types of machines can make excellent espresso, but rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler makes the water warm to the right temperature to extract. The resulting steam reaches the portafilter containing the ground espresso coffee, and gets funnelled down into the cup. The steam generates enough pressure to push the coffee grounds through. This results in a whipped-up top of the espresso. This is one of the main characteristics of a great buy espresso machines.

There are three different types of espresso machines, each having different types of pumps and the temperature of the brew. There are a variety of ways that the brew may be controlled, as well as the size of the cup the machine is capable of making.

The earliest espresso machines were steam types. They had one boiler to create both steam and brew, but the pressure they could produce was very low - just two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most common espresso machine is a semiautomatic model with an electric pump. These are what people imagine when they think of an espresso maker. Semi-automatic machines require you to grind and tamp your beans yourself however the pump controls the flow of water and pressure. This is an excellent compromise between human touch and mechanized consistency.

The Filter

Espresso machines usually have filters that separate the grounds of coffee from hot water. The filter is also a vital part of the temperature control system as it keeps the machine from overheating.

A filter also helps with flavor, as it permits the beans to flower for a longer period of time. This allows beans to release their flavor and gives an opportunity to improve extraction.

However, it is important to keep in mind that even a high-quality filter can make a terrible cup of coffee as the quality of the beans and extraction are crucial.

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

Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then moves hot water through the grounds of coffee at high pressure. They are less expensive and easier to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, espresso machine with grinder machines driven by compressed air-pump are becoming increasingly popular. They use an air-compressor to push hot water across the ground and are much more mobile than steam-driven electric espresso machines.