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How Does machines espresso machines ? Machine espresso makes use of precise pressure and amazing filter technology to make the coffee we love. How exactly does it work? Espresso is made 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 Group Head As the name implies the group head is the place you insert your portafilter when making espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the extraction. There are various kinds of group head, each with their particular advantages and disadvantages. Some focus on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. There are also some that have a combination 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 above photo the group head is made up of many notches in which you can place your portafilter and twist it by hand to lock it in. A gasket made of rubber is placed in the notches to create a seal when you insert your portafilter. The notches allow for precise placement of the portafilter. This is vital for an even extraction. The group head not only lets you to insert your portafilter easily however it also keeps the same temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is constant for extraction. It is important to remember that even a small deviation can make the difference between a decent and a excellent espresso. The Pump The motorized pumps used in espresso machines rotary provide nine atmospheric bars of pressure required for espresso extraction. This differs from manual piston machines that rely on a lever. This pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger before being pumped through the ground coffee inside the group head. Pumps are typically less expensive than piston-driven machines and tend to last longer, although both types of machines may get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, which could increase prices of even simpler models. Some espresso machines can eliminate the pump completely and utilize steam pressure to make espresso. This can lead to over-extraction as the boiler that makes steam also heats the water until it comes to a boil. These machines also have to constantly rebuild their pressure between cups. This requires energy and time. Many espresso machines make use of an rotary or a vibration pump. A vibration model utilizes a rotating disk to generate pressure, whereas a rotary model pushes hot water through the ground at a high speed. Both machines produce great espresso, but rotary machines are more stable, quieter and less likely to break. The Boiler The boiler is the part that heats water to an ideal temperature for extraction. The resulting steam reaches the portafilter containing the ground espresso coffee and is then pumped into the cup. The steam creates enough pressure to push the grounds of coffee through. This results in a whipped-up top of the espresso. This is the hallmark of a good espresso. There are three kinds of espresso makers. They differ in the type of pump they employ and how hot the espresso is. There are various ways to control the strength of the brew and the size of cup that can be produced by the machine. The first espresso machines were steam-types. They employed a single boiler to make both steam and brew but the pressure they could produce was very low – just two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. The modern espresso machine was developed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni. The most commonly used espresso maker is a semi-automatic machine that has an electric pump. These are the things people think of when they think of an espresso machine. If you have a semi-automatic machine you must grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is a great compromise between human control and mechanised reliability. The Filter Typically, espresso machines utilize filters that separate the coffee grounds as they pass through the hot water. The filter is also a vital element of the temperature control system, as it prevents the machine from overheating. It also improves flavor, as a filter can allow for a longer bloom phase. This helps the beans release their nuances 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, and the extraction process are still very important. This is where the magic happens. It's what makes an espresso really taste great. The grouphead, sometimes called the brew head, is the place where the portafilter (the thing you put the ground coffee in) sits when you're making espresso. In an espresso machine that is driven by steam, hot water is heated in an airtight container to produce steam, which is then pushed through the grounds at a high pressure. These kinds of machines tend to be less expensive and simpler to maintain than pump-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 perfect shot requires 9-10 bars. In recent years, compressed air-pump-driven espresso machines have become more popular. They use an air compressor to force hot water into the ground, and are more mobile than steam-driven electric espresso machines.