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How Does Machine Espresso Work? Machine espresso utilizes precise pressure and amazing filter technology to make the coffee we love. How exactly does it work? Espresso is created by forcing hot water under high pressure through finely-ground coffee. The process is similar to that of 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 espresso. It disperses the water into the portafilter, and then regulates the pressure of the extraction. There are various kinds of group head each with its particular advantages and disadvantages. Some focus on temperature stability, some on pre-infusion features, and others are designed to control the lever. There are some that contain a variety of features, like the E61 one, which is the standard choice for many baristas because of its ability to offer multiple perks in one package. As you can see in the image above the group head has a number of notches. best espresso machine is placed into these notches and turn the head around to secure it. There is also a rubber gasket which is located inside the notches to help create the seal when you insert your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is essential to ensure a consistent extraction. The group head not only allows the portafilter to be inserted easily but also maintains an even temperature. It does this by cycling hot water through the brew pan and around the portafilter, ensuring that it's always at the correct temperature for extraction. This is important, as even a few degrees can make the difference between a excellent and great espresso. The Pump In contrast to piston machines that are manually operated, that use a lever to pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure required to extract espresso. The pressure is created by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being pumped through the ground coffee in the group head. Pumps tend to be cheaper than piston-driven models, and they tend to last longer. However, both types of machine can be damaged by excessive use and inadequate cleaning. Pumps are also more complicated mechanically, which could increase prices of even simple models. Some espresso machines make use of steam pressure instead of a pump to brew espresso. The downside is that the boiler that produces steam also raises the temperature of water to boiling which could lead to excessive extraction. Additionally, these machines frequently have to rebuild their pressure between cups, which requires time and energy. Many espresso machines utilize an rotary or vibrating pump, with a vibration model using a rotating disc to create pressure and rotating models that push hot water through the grounds at high speed. Both types of machine can make excellent espresso, but rotary machines are quieter and more durable than vibration pumps. The Boiler The boiler is the one that will heat the water to a temperature that is ideal to extract. The resultant steam then reaches the portafilter that contains the ground espresso and is then pumped down into the cup. During this process, the steam causes pressure to push through the grounds of the coffee. This produces a layer of crema on top. This is a hallmark 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 various ways that the brew can be controlled and the size of the cup that the maker can create. The earliest espresso machines were steam type. They employed one boiler to create both steam and brew however, the pressure they could produce was very low – just two bars of atmospheric pressure at the most. This led to the coffee tasting burnt and bitter. This is the reason why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created 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 envision these machines. With a semi-automatic machine you must grind the beans and tamp them by hand. However, the pump is able to regulate the flow of water and pressure. This is a perfect combination of human control and mechanised consistency. The Filter Typically, espresso machines use filters to separate the coffee grounds as they pass through the hot water. The filter is also an important part of the temperature control system, as it keeps the machine from overheating. It also improves flavor, since a filter allows for a longer bloom phase. This helps the beans to release their flavor and gives the chance for better extraction. It is important to keep in mind that even the finest filter can make a bad cup of coffee. The quality of the beans as well as the extraction, are still very important. It's in this area that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead, also referred to as the brewhead, is where the portafilter (the thingy you put the ground coffee in) sits when you're making espresso. In a steam-driven espresso machine hot water is heated in an airtight container to produce 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. They are however limited in their ability for creating the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars. In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They use an air-compressor to push hot water through the ground, and are more mobile than electric steam-driven espresso machines.