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How Does Machine Espresso Work? The machine espresso uses precise pressure, as well as a filtering technology that is amazing to create the coffee you love. But how exactly does it work? Espresso is created by forcing hot water under high pressure through finely-ground coffee. The process is similar to making drip coffee but the key difference is in the pressure. The Head of the Group The name implies, the group head is where you place your portafilter while making espresso. It disperses water in the portafilter and regulates the pressure of extraction. There are various kinds of group head each with its unique advantages and disadvantages. Some are designed for stability of temperature while others are designed to handle pre-infusion. Some are designed to control the lever. Some have a combination, like the E61. This is a favorite among baristas because it offers multiple benefits in a single package. As you can see from the above photo the group head has a number of notches. You can place your portafilter inside these notches, and then twist the head to lock it. A gasket of rubber is situated inside the notches, which helps create a seal as you insert your portafilter. The notches on the head allow for a precise location of the portafilter which is necessary for an even extraction. Apart from allowing you easily place your portafilter in, the group head is responsible to ensure that the temperature remains even. This is achieved by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is always at the right level to extract the coffee. It is crucial to keep in mind that even a slight variation can mean the difference between a decent and a excellent espresso. The Pump The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure needed to extract espresso. coffeee.uk differs from manual piston machines which use a lever. This pressure builds up by removing tap water from a reservoir and pumping it through a heat exchanger before being pumped through the ground coffee in the group head. Pumps are generally cheaper and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading because of excessive use and insufficient cleaning. They also create mechanical complexity and can lead to the cost of even the most basic models. Certain espresso machines do away with the pump completely and employ steam pressure to create espresso. This could lead to over-extraction since the boiler that produces steam also heats the water to boil. The machines also need to continuously rebuild their pressure between cups. This requires energy and time. Many espresso machines employ the rotary or vibration pump, which has a vibration model that uses a vibrating disc to create the pressure, and rotating models that push hot water through the grounds at high speed. Both models can make a great espresso, but the rotary pumps are quieter, and more durable than vibration pumps. The Boiler The boiler will heat the water to the perfect temperature to extract. The steam created will eventually reach the portafilter, which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process, steam creates pressure that pushes through the grounds of the coffee. This results in a layer crema that is then poured over. This is one of the hallmarks of a great espresso. There are three distinct types of espresso machines, each having distinct pumps and brew temperature. There are various ways to control the amount of brew, as well as the size of cup that can be produced by the machine. The earliest espresso machines were steam type. The first espresso machines were steam-type machines. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni. The most popular espresso machine is a semiautomatic model with an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans on your own while the pump controls the flow of water and pressure. This is a perfect combination of human control and mechanised accuracy. The Filter Espresso machines typically use a filter that separates the grounds of the coffee from hot water. The filter is also an essential part of the machine's temperature control, as it prevents overheating. It also aids in flavor, as a filter allows for a longer bloom time. This allows the beans to release their flavors, and improves extraction. However, it is important to remember that even a great filter can make a terrible cup of coffee, because the quality of the beans and extraction is still crucial. It's here that the magic happens. This is the reason why espresso tastes so good. The grouphead (also known as the brewhead) is where you place the portafilter, the device that you use to put the grounds of your coffee into while making espresso. Steam-driven espresso machines make use of hot water that is heated in an airtight container to produce steam. The steam then pushes hot water through grounds of the coffee under pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. However, they are limited in their ability to create the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar. In recent years, espresso machines driven by compressed air-pump are becoming increasingly popular. They utilize an air compressor to push hot water through the ground. They are also more mobile than steam-driven electric espresso machines.