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How Does Machine Espresso Work? Machine espresso makes use of precise pressure and mind-blowing filter technology to create the coffee we love. But 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 main difference lies in the pressure. The Group Head As the name implies, the group head is where you place your portafilter while making espresso. It distributes water into the portafilter, and regulates the pressure of the extraction. There are various kinds of group head, each with their distinct advantages and disadvantages. Some are focused on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some include a combination such as the E61. This is a favorite among baristas since it provides multiple advantages in a single package. As you can see in the above image, the group head has numerous notches that you can place your portafilter and twist it manually to secure it. A gasket of rubber is situated within the notches to make a seal when you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is crucial for an efficient extraction. The group head does not just allow the portafilter to be inserted easily but also maintains the temperature at a constant level. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it's always at the correct temperature for extraction. This is vital, because even a small difference in temperature can make the difference between good and excellent espresso. The Pump The motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure that is required for espresso extraction. This is different from manual piston machines which use levers. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the ground coffee inside the group head. Pumps are typically more affordable and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading because of frequent use and poor cleaning. They also create mechanical complexity which can result in costly prices for even the most basic models. Certain espresso machines eliminate the pump completely and utilize steam pressure to make espresso. The drawback of this is that the same boiler that produces steam also increases the temperature of the water to the point of boiling, which can lead to excessive extraction. These machines also have to constantly rebuild their pressure in between cups. This requires energy and time. Many espresso machines employ a vibration or rotary pump, with a vibration model that uses a vibrating disc to create pressure, and an rotary model that pushes hot water through the grounds at high speed. Both types of machine can make a great espresso, but Rotary machines are quieter and more durable than vibration pumps. The Boiler The boiler is the one that heats the water to the perfect temperature for extraction. The resulting steam is then transferred to the portafilter containing the ground espresso and is then funneled down into the cup. During this process, the steam creates pressure and pushes through the grounds of the coffee. espresso machines for home produces a layer of crema that is then poured over. This is one of the hallmarks of a good espresso. There are three different types of espresso machines, each with a different type of pump and brew temperature. There are many ways to control the brew as well as the size of the cup that can be produced by the machine. The first espresso machines were steam-type. They had one boiler to make both brew and steam, however the pressure they were able to produce was not very high – two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni. The most commonly used espresso machine is a semiautomatic that has an electric pump. These are the images people have when they think of an espresso machine. If you have a semi-automatic machine you must grind the beans and tamp them yourself but the pump is able to regulate the flow of water and pressure. This is a perfect solution that combines human control with mechanised consistency. The Filter Typically, espresso machines use filters to separate the grounds of coffee as they move through the hot water. The filter is also a vital part of the machine's temperature control, since it stops overheating. A filter also helps with flavor as it allows for an extended flowering time. This lets the beans release their nuances, and allows for better extraction. However it is crucial to keep in mind that even a top filter can make a terrible cup of coffee, as the quality of the beans and extraction is still crucial. This is where the magic happens, it's the thing that makes espresso taste great. The grouphead (also known as the brewhead) is where you put the portafilter, which is the thingy used to place the coffee grounds into, 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 with high pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars. In recent years, espresso machines driven by compressed air-pump have become increasingly popular. They use an air compressor to force hot water through the grounds, and are far more portable than steam-driven electric machines.