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How Does Machine Espresso Work? The machine espresso is made using precision pressure, and a filtering system that is awe-inspiring to create the coffee you enjoy. How does it work exactly? Espresso is produced by pushing hot water under pressure through finely ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure. The Head of the Group As the name implies the group head is where you insert your portafilter when brewing espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure that results from the extraction. There are several different types of group head each with its particular advantages and disadvantages. Some are focused on temperature stability, some on pre-infusion features, and others are designed to control the lever. There are even some that have a combination of features, like the E61, which is considered the classic choice among many baristas due to its ability to provide multiple benefits in one package. As you can see in the photo above the group head is made up of numerous notches that you can place your portafilter and twist it with your hands to secure it. A gasket made of rubber is positioned in the notches to create a seal as you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is vital for an efficient extraction. The group head is not just able to allow the portafilter to be inserted easily, but it also maintains a constant temperature. This is done by cycling hot water around the portafilter, and through the brew basin, ensuring the temperature is always right for extraction. This is crucial, since even a small difference in temperature can make the difference between a good and excellent espresso. The Pump The motorized pumps used in rotary espresso machines provide the nine atmospheric bar pressure needed to extract espresso. This is different from manual piston machines that rely on a lever. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger prior to being shot through the ground coffee inside the group head. Pumps tend to be less expensive than piston-driven machines and tend to last longer, but both types of machines can become damaged due to excessive use and poor cleaning. They also create mechanical complexity and can lead to a high price tag on even the simplest models. Certain espresso machines utilize steam pressure instead of a pump to brew espresso. The downside is that the same boiler that produces steam also raises the temperature of water to the point of boiling which can cause over-extraction. In addition, these machines frequently have to restore their pressure between cups, which takes time and energy. A large majority of espresso machines employ the rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, while a Rotary model pushes hot coffee through the ground at high speed. Both types of machines can make excellent espresso, but the rotary models are quieter and more durable than vibration pumps. The Boiler The boiler is the one that is used to heat the water to the ideal temperature for extraction. The steam that is produced reaches the portafilter that contains the ground espresso and is then pumped into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This results in a layer of crema that is then poured over. This is one of the main characteristics of a good espresso. There are espresso coffee maker of espresso machines, each with different types of pumps and brew temperature. There are different ways to control the strength of the brew and the size of the cup that can be made by the machine. The earliest espresso machines were steam types. They had one boiler to create steam and brew, however, the pressure they could produce was very low – just two bars of atmospheric pressure at the most. This resulted in the coffee tasting bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine. The most popular espresso machine is a semiautomatic with an electric pump. These are what people imagine when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the water flow and pressure. This is an excellent combination of human control and mechanized consistency. The Filter Typically, espresso machines employ a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a crucial element of the temperature control system since it helps prevent the machine from overheating. It also improves flavor, as it lets you enjoy a longer bloom time. This lets the beans release their nuances, and also allows for better extraction. It is important to keep in mind that even the most efficient filter could result in a poor cup of coffee. The quality of the beans, and the extraction process are still very important. It's here that the magic takes place. This is the reason why espresso tastes so good. The grouphead, also called the brewhead, is where the portafilter (the container you place the ground coffee in) is placed when making espresso. In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. This is then pushed through the grounds at a high pressure. These kinds of machines are typically cheaper and easier to maintain than pump-driven models. However, they are limited in their ability to produce the perfect brewing conditions because they operate 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 been gaining popularity. They utilize an air compressor to push hot water through the grounds and are significantly more portable than steam-driven electric machines.