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How Does Machine Espresso Work? Machine espresso utilizes precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it? To make an espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to that of making drip coffee. However, the pressure is the major difference. The Head of the Group The group head is the portafilter you insert when brewing espresso. It disperses water into the portafilter, and then regulates the pressure during the extraction. There are various kinds of group heads, each with their particular advantages and drawbacks. Some focus on temperature stability, others on pre-infusion capabilities, while others are designed to control the lever. There are even some that include a mix of features, like the E61, which is the classic choice among many baristas due to its ability to provide multiple benefits in one package. As you can see in the above photo, the group head is fitted with a variety of notches. You place your portafilter in these notches, then twist the head to secure it. There is also a gasket made of rubber that resides inside the notches to help create an airtight seal after inserting your portafilter into the machine. The notches permit the precise placement of the portafilter. This is vital for an accurate extraction. Aside from allowing you to easily connect your portafilter, the group head is responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket, and around the portafilter to ensure that it's always at the right temperature for extraction. espresso machines uk is important to realize that even a few degree differences can make the distinction between a good and excellent espresso. The Pump In contrast to manual piston machines that use a lever to pressurize water, rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger prior to it is shot through the ground coffee inside the group head. Pumps are typically less expensive and last longer than piston-driven machines. However, both kinds of machines can deteriorate because of excessive use and insufficient cleaning. They also increase the complexity of mechanical systems that can lead to costly prices for even the most basic models. Certain espresso machines can eliminate the pump completely and instead use steam pressure to brew espresso. This could lead to over-extraction since the boiler that makes steam also heats the water to boil. In addition, these machines frequently have to restore their pressure between cups, which takes time and energy. A majority of espresso machines use an rotary or vibrating pump, with a vibrating model using a rotating disc to generate the pressure and an rotary model that pushes hot water through the grounds under high speed. Both machines can make great espresso, but rotary machines are quieter, more durable and less likely to fail. The Boiler The boiler is the one that makes the water warm to a temperature that is ideal to extract. The resultant steam then reaches the portafilter that contains the ground espresso and gets funnelled down into the cup. During this process the steam causes enough pressure to push the coffee grounds through. This creates a foam on top of the espresso. This is one of the main characteristics of a good espresso. There are three distinct types of espresso machines, each with distinct pumps and the temperature of the brew. There are various ways to control the brew and the size of cup that can be made by the machine. The first espresso machines were steam types. They used one boiler to make both steam and brew, however the pressure they were able to create was minimal – two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. This is the reason why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine. The most common espresso maker is a semiautomatic machine that has an electric pump. These are the images people have when they imagine 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 compromise between human control and mechanised accuracy. The Filter Typically, espresso machines use a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also a crucial component of the temperature control system because it stops the machine from overheating. Filters also aid in flavor, as it permits a longer flowering phase. This allows beans to release their flavor and gives an opportunity for a better extraction. However, it is important to remember that even a high-quality filter can produce a bad cup of coffee, since the quality of the beans and extraction are crucial. It's here that the magic occurs. This is what makes espresso taste so delicious. The grouphead (also known as the brewhead) is where you put the portafilter, the thingy that you use to put the grounds of coffee into when making espresso. Steam-driven espresso machines make use of hot water heated in an airtight container to create steam. The steam then pushes hot water through the grounds of coffee under high pressure. These kinds of machines are usually less expensive and simpler to maintain than pumps-driven models. However, they are not as efficient in their ability to produce the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure. The perfect shot requires 9-10 bars. In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They use an air compressor to push the hot water through the grounds and are much more portable than electric steam-driven machines.