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How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and amazing filter technology to make the perfect cup of coffee. But how exactly does it work?

To make an 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

The group head is the portafilter that is inserted when you are making home espresso machine. It disperses the water into the portafilter, and then regulates the pressure during the extraction. There are many different kinds of group heads each with its distinct advantages and disadvantages. Some are specifically designed for stability of temperature while others are designed to handle pre-infusion. Others are built to control the lever. Some have a combination of features, like the E61, which is considered the most popular choice among baristas because of its ability to offer multiple perks in a single package.

As you can see in the image above the group head is made up of several notches to place your portafilter and twist it with your hands to secure it. A gasket of rubber is situated inside the notches, which helps make a seal when you insert your portafilter. The notches permit precise placement of your portafilter. This is essential for an accurate extraction.

The group head not only lets you to place your portafilter easily however, it also keeps the temperature at a constant level. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is at the right level for extraction. It is important to remember that even a slight differences can make the distinction between a good and great espresso.

The Pump

Unlike manual piston machines, that use a lever to pressurize water, rotary best cheap espresso machine machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary to extract espresso. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally less expensive than piston-driven machines, and tend to last longer, although both types of machines could get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, and can add to prices of even simpler models.

Certain espresso machines do away with the pump completely and 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 could lead to over-extraction. The machines also need to continuously rebuild their pressure between cups. This takes energy and time.

A large majority of espresso maker Barista machines employ a rotary or vibration pump. A vibration model utilizes an oscillating disk to create pressure, while the circular model pushes hot liquid through the ground at a high speed. Both types of machine can make a great espresso, however rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the part that heats the water to the optimal temperature to extract. The steam produced is then directed to the portafilter, which is the container that holds the espresso coffee grounds. It is then pumped into the cup. The steam causes enough pressure to push the grounds of the coffee through. This results in a crema on top of the espresso. This is the hallmark of a good espresso.

There are three different types of espresso machines, each with distinct pumps and the temperature of the brew. There are various ways that the brew can be controlled as well as the dimensions of the cup the machine can make.

The first espresso machines were steam-types. The first cheap espresso machine machines were steam-type machines. This led to the coffee tasting bitter and burnt. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic machine you have to grind the beans and tamp them by hand. However, the pump provides regulated water flow and pressure. This is an excellent combination of human control and mechanized consistency.

The Filter

Espresso machines typically use a filter that separates the grounds of the coffee from the hot water. The filter is also a crucial part of the temperature control system, as it prevents the machine from overheating.

It also enhances flavor as a filter allows for a longer bloom time. This lets the beans let their nuances out, and allows for a better extraction.

However, it is important to keep in mind that even a top filter can produce a bad cup of coffee, as the quality of the beans and extraction are vital.

This is where the magic happens, and it's what makes espresso taste great. The grouphead (also called the brewhead) is where you put the portafilter, which is the thingy used to place the coffee grounds into, while making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. Steam is then pushed through the grounds at high pressure. They are less expensive and easier to maintain than pumps-driven models. They are however limited to create the perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water through grounds and are significantly more portable than steam-driven electric machines.