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How Does Machine Espresso Work?

Machine Espresso (Wikimapia.Org) employs precise pressure and incredible filter technology to produce the coffee we love. What exactly does it work?

espresso machine with milk frother is made by pushing hot water at high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the main difference.

The Head of the Group

As the name implies, the group head is where you put your portafilter in when making espresso. It disperses the water into the portafilter, and regulates the pressure of extraction. There are many different kinds of group head, each with their particular advantages and disadvantages. Some focus on temperature stability, some on pre-infusion options, and others are designed to control the lever. There are even some that come with a range of features, like the E61 one, which is the classic choice among many baristas for its ability to offer multiple perks in a single package.

As you can see in the above photo the group head comes with many notches in which you can put your portafilter, then twist it with your hands to secure it. A gasket of rubber is situated inside the notches to help make a seal when you insert your portafilter. The notches on the head allow for an exact positioning of the portafilter which is necessary for a consistent extraction.

The group head does not just allow you to insert your portafilter easily but also maintains an even temperature. It does this by circulating hot water through the brew container and around the portafilter, making sure that it's always at the correct temperature to extract. This is important, as just a few degrees could be the difference between a good and excellent espresso.

The Pump

Unlike manual piston machines, which rely on a lever to pressurize water, rotary espresso 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 prior being shot through the ground coffee inside the group head.

Pumps are generally less expensive and last for longer than piston-driven machines. However, both kinds of machines may degrade due to excessive use and insufficient cleaning. Pumps are also more complex mechanically, and can add to the cost of even the most basic models.

Certain retro espresso maker machines do away with the pump entirely and make use of steam pressure to make espresso. The disadvantage of this is that the boiler that produces steam also raises the temperature of the water until it reaches boiling, which can lead to over-extraction. Additionally these machines are often required to rebuild their pressure between cups, which takes time and energy.

Many espresso machines utilize either a rotary or vibration pump, with a vibrating model using a rotating disc that generates the pressure, and a rotary model pushing hot water through the grounds under high speed. Both types of machine can make a great espresso, but the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is the component that heats water to an optimal temperature to extract. The steam that is created will eventually reach the portafilter, which contains the espresso coffee grounds. It is then poured into the cup. During this process the steam generates enough pressure to push the grounds of the best coffee espresso machine through. This results in a whipped-up top of the espresso. This is a sign of a good espresso maker barista.

There are three kinds of espresso makers. They differ in the type of pump they employ and how hot the coffee is. There are a variety of ways to control the brew and the size of the cup that can be produced by the machine.

The earliest espresso machines were steam-based. The earliest espresso machines were steam-type machines. The coffee tasted bitter and burnt. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso maker is a semi-automatic one with an electric pump. This is what people envision when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is a fantastic combination of human control and mechanised accuracy.

The Filter

Typically, espresso machines have filters to separate the grounds of coffee as they move through the hot water. The filter is also an essential component of the machine's temperature control, since it stops overheating.

It also improves flavor, as it allows for a longer bloom time. This lets the beans release their flavors, and allows for better extraction.

However, it is important to remember that even a good filter can produce a bad cup of coffee, as the quality of the beans and extraction are crucial.

It's here that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you place the portafilter, the thingy that you use to put the coffee grounds into, when making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam, which then pushes the hot water through the grounds with high pressure. These machines are less expensive and easier for the user to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the ideal brewing conditions, since they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar.

In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They make use of an air compressor to push hot water across the ground, and are more mobile than steam-driven electric espresso machines.