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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and amazing filter technology to make the coffee we love. What exactly is it?

In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to 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 place your portafilter while brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the resulting extraction. There are a variety of types of group heads each with its distinct advantages and drawbacks. Some are designed for temperature stability while others are built to handle pre-infusion. Others are built to control the lever. Some have a combination of features, like the E61 that is the classic choice among many baristas due to its ability to offer multiple benefits in a single package.

As you can see in the image above the group head has a number of notches. You can place your portafilter into these notches and twist the head to lock 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 location of the portafilter which is necessary for an even extraction.

Apart from allowing you easily place your portafilter in, the group head is also responsible to maintain an even temperature. It does this by circulating hot water through the brew basket and around the portafilter, ensuring that it's always at the correct temperature to extract. It is crucial to keep in mind that even a few degree difference can make the difference between a good and a excellent commercial espresso machine.

The Pump

Contrary to manual piston machines which use 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 pumping water through a heat exchanger and then through the ground coffee.

Pumps are typically less expensive than piston-driven machines and tend to last longer, however both types of machine can be damaged by excessive use and inadequate cleaning. They also create mechanical complexity that can lead to an expensive price for even the most basic models.

Certain espresso machines can eliminate the pump completely and instead employ steam pressure to create espresso. The drawback of this is that the boiler that produces steam also raises the temperature of water to the point of boiling which can cause excessive extraction. Additionally these machines typically have to restore their pressure between cups, which takes time and energy.

Many espresso machines use an rotary or a vibration pump. A vibration model employs the vibrating disk to create pressure, while the rotating model pushes hot water through the ground at a rapid speed. Both types of machine are capable of producing excellent espresso home machine, however the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is what heats the water to the ideal temperature to extract. The steam that is produced gets to the portafilter which contains the espresso coffee grounds. It is then funneled into the cup. The steam generates enough pressure to push the coffee grounds through. This results in a layer of crema on top. This is a sign of a great espresso coffee maker.

There are three kinds of commercial espresso machine makers. They differ in the kind of pump they use and the degree of heat that the coffee is. There are also different ways that the brew can be controlled and the size of the cup that the machine can make.

The earliest espresso machines were steam-based. They used only one boiler to make steam and brew, but the pressure they could produce was not very high - two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic espresso machine, you grind the beans and then tamp them by hand. However, the pump provides regulated water flow and pressure. This is a fantastic solution that combines human control with mechanised reliability.

The Filter

Espresso machines typically use filters that separate the grounds of coffee from hot water. The filter is also an important component of the temperature control system because it stops the machine from overheating.

A filter also helps with flavor since it allows for a longer flowering phase. This allows beans to release their flavor and gives an opportunity to improve extraction.

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

This is where the magic happens. It's what makes espresso taste great. The grouphead, often called the brewhead, is where the portafilter (the thing you put the coffee grounds into) is located when you're 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 cheaper and are easier for the user to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the ideal conditions for brewing as they only operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bars.

In recent years, compressed-air-pump-driven espresso machines have become more popular. They utilize an air compressor to force hot water into the grounds and are much more portable than steam-driven electric machines.