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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to make the coffee we love. But how exactly does it work?

Espresso is made by forcing hot water under 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 group head is the portafilter is inserted when you are making espresso. It disperses the water into the portafilter, and then regulates the pressure of extraction. There are various kinds of group heads, each with their own advantages and disadvantages. Some focus on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. Some have a combination, such as the E61. This is a very popular choice for baristas since it provides multiple benefits in one package.

As you can see from the picture above the group head is fitted with several notches. You can place your portafilter inside these notches, and then twist the head to secure it. A gasket of rubber is situated in the notches to create a seal while you insert your portafilter. The notches allow for an exact placement of the portafilter. This is essential for a consistent extraction.

Apart from allowing you easily connect your portafilter, the group head is also responsible to ensure that the temperature remains even. It does this by cycling hot water through the brew pan and around the portafilter, ensuring that it is always at the correct temperature to extract. This is crucial, since just a few degrees could be the difference between a good and excellent espresso.

The Pump

The motorized pumps that are used in rotary espresso machines provide the nine atmospheric bar pressure required for espresso extraction. This differs from manually operated piston machines that employ levers. The pressure is built 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, but both types of machine can degrade with overuse and insufficient cleaning. They also create mechanical complexity that can lead to an expensive price for even the simplest models.

Some espresso machines can eliminate the pump completely and make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that makes steam also causes the water to boil. In addition these machines are often required to restore their pressure between cups, which requires time and energy.

Many espresso machines employ either a rotary or vibration pump, with a vibrating model using a vibrating disc to generate the pressure, and the rotary model pushing hot water through the grounds under high speed. Both models are capable of producing excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler heats the water to a temperature that is ideal to extract. The steam created is then directed to the portafilter, which is the container that holds the espresso coffee grounds. It is then pumped into the cup. During this process, steam creates pressure to push through the coffee grounds. This creates a foam on top of the espresso. This is a sign of a great espresso.

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

The earliest espresso machines were steam type. They employed a single boiler to make both brew and steam, but the pressure they could generate was low - only two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most commonly used espresso maker is a semi-automatic one that has an electric pump. These are the images people have when they think of an espresso maker. If you have a semi-automatic machine you have to grind the beans and then tamp them by hand. The pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized quality.

The Filter

Typically, espresso machines use filters to separate the grounds of coffee when they pass through the hot water. The filter is also an essential element of the temperature control system, since it helps prevent the machine from overheating.

A filter can also help with flavor because it allows for an extended flowering time. This allows beans to let their nuances out and provides an opportunity for a better extraction.

It is important to remember that even the best filter can produce a bad cup of coffee. The quality of the beans, as well as the extraction, remain vital.

This is where the magic happens, it's what makes an espresso machine sale really taste great. The grouphead, often referred to as the brew head, is where the portafilter (the device you put the ground coffee in) sits when you're making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water into the grounds of coffee at high pressure. These machines are cheaper and easier for the user to maintain than pumps-driven models. However, they are not as efficient in their ability to create the perfect conditions for brewing, since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.

In recent years, compressed air-pump-driven espresso machines have become more 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.