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How Does Machine Espresso Work?

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

To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However the pressure is the main difference.

The Group Head

The group head is the portafilter that is inserted when you are making espresso. It disperses water into the portafilter, and then controls the pressure of the extraction. There are several different types of group head, each with their unique advantages and disadvantages. Some focus on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. There are some that include a mix of features, like the E61 one, which is the classic choice among many baristas because of its ability to offer multiple perks in one package.

As you can see in the picture above the group head has a number of notches. You can place your portafilter inside these notches, and then twist the head to secure it. A rubber gasket is located in the notches to create a seal when you insert your portafilter. The notches on the head allow for an exact position of the portafilter which is vital for an efficient extraction.

The group head is not just able to allow you to put in your portafilter easily however it also keeps a constant temperature. It does this by cycling hot water through the brew container and around the portafilter to ensure that it's always at the right temperature for extraction. This is important, as even a small difference in temperature can make the difference between a good and great espresso.

The Pump

The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure required for espresso extraction. This differs from manual piston machines that rely on a lever. The pressure is built by pumping water through a heat exchanger and then through the ground coffee.

Pumps tend to be cheaper than piston-driven machines, and they tend to last longer, however both types of machines could get damaged through overuse and lack of cleaning. Pumps are also more complex mechanically, and can add to the cost of even most basic models.

Some espresso machines employ steam pressure instead of a pump to make espresso. The downside is that the same boiler that produces steam also raises the temperature of the water to boiling, which can lead to excessive extraction. The machines also need to continually rebuild their pressure between cups. This requires energy and time.

A majority of espresso machines use the rotary or vibration pump, which is a vibration model that uses a vibrating disc to create the pressure and an rotary model that pushes hot water through the grounds at high speed. Both machines espresso can make great espresso, but rotary machines are quieter, more durable and less likely to break.

The Boiler

The boiler is the component that heats water to the ideal temperature for extraction. The steam that is produced reaches the portafilter, which contains ground espresso beans and is then pumped down into the cup. In this process, the steam creates pressure to push through the grounds of the coffee. This results in a layer of crema that is then poured over. This is one of the hallmarks of a good espresso.

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

The first espresso machines were steam-types. They had a single boiler to make both brew and steam, however the pressure they were able to generate was low - only two bars of atmospheric pressure maximum. This led to the coffee tasting bitter and burnt. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most commonly used espresso maker is a semi-automatic machine that has an electric pump. When people think of espresso machines, they imagine these machines. If you have a semi-automatic machine you need to grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is an excellent compromise between human touch and mechanized quality.

The Filter

Typically, espresso machines have a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also an essential part of the machine's temperature control, as it helps prevent overheating.

It also aids in flavor, as it allows for a more prolonged bloom phase. This allows the beans to release their flavor and also allows for Machines Espresso better extraction.

It is important to remember that even the finest filter can make a bad cup of coffee. The quality of the beans and the extraction process remain vital.

It's in this area that the magic occurs. This is what makes espresso taste so delicious. The grouphead (also called the brewhead) is where you place the portafilter, which is the thingy that you use to put the grounds of your best coffee espresso machine into when making espresso.

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

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