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How Does Machine Espresso Work?

The machine espresso is made using precise pressure, as well as a filter technology that is awe-inspiring to make the coffee you enjoy. But how exactly does it work?

To make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.

The Head of the Group

The name implies, the group head is the place you place your portafilter while brewing espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the resulting extraction. There are a variety of types of group heads, each with their unique advantages and disadvantages. Some are designed for stability in temperature, while others are designed to handle pre-infusion. Others are built to control the lever. There are some that have a combination of features, such as the E61, which is considered the standard choice for many baristas due to its capacity to offer multiple benefits in a single package.

As you can see from the above photo the group head is fitted with several notches. It is possible to place your portafilter inside these notches, and then turn the head around to secure it. A gasket made of rubber is positioned inside the notches to help make a seal when you insert your portafilter. The notches allow for the precise placement of the portafilter. This is crucial to ensure an efficient extraction.

The group head not only lets you to insert your portafilter easily however it also keeps the temperature at a constant level. It does this by circulating hot water through the brew pan and around the portafilter to ensure that it's always at the correct temperature for extraction. This is important because just a few degrees could mean the difference between good and excellent Espresso machine small.

The Pump

Unlike manual piston machines, which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps to provide the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being pushed through the ground coffee in the group head.

Pumps are generally less expensive and last for longer than piston-driven machines. However, both kinds of machines may degrade because of frequent use and insufficient cleaning. They also add mechanical complexity and can lead to the cost of even the simplest models.

Some espresso machines eliminate the pump entirely and make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that produces steam also heats the water until it comes to a boil. The machines must also continually rebuild their pressure between cups. This requires energy and time.

Many espresso machines utilize a vibration or rotary pump, which has a vibration model using a rotating disc to create pressure, and an rotary model that pushes hot water through the grounds under high speed. Both machines can produce excellent espresso, however rotary machines are more stable, quieter and less likely to break down.

The Boiler

The boiler is what is used to heat the water to the perfect temperature for extraction. The steam created is then directed to the portafilter, which contains the espresso coffee grounds. The steam is then channeled into the cup. The steam creates pressure and pushes through the grounds of the coffee. This creates a crema on top of the espresso. This is one of the hallmarks of a great espresso.

There are three types of espresso makers, which differ in the type of pump they use and the degree of heat that the espresso is. There are various ways to control the brew and the size of the cup that can be made by the machine.

The first espresso machines were steam types. They had only one boiler to make both brew and steam, but the pressure they could generate was low - only two bars of atmospheric pressure at most. This led to the coffee tasting burnt and bitter. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

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

The Filter

Espresso machines usually have filters that separate the grounds of the coffee from the hot water. The filter is also an essential part of the machine's temperature control, as it prevents overheating.

It also helps with flavor as a filter allows for a longer bloom phase. This helps the beans release their flavors and provides an opportunity for better extraction.

It is important to remember that even the finest filter can result in a bad cup of coffee. The quality of the beans as well as the extraction, are still very important.

This is where the magic happens, it's what makes an espresso really taste great. The grouphead, also referred to as the brewhead, is where the portafilter (the device you put the ground coffee in) is placed when making espresso.

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

In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They use an air compressor to push hot water through grounds and are more portable than steam-driven electric espresso maker machines.