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How Does Machine Espresso Work? Machine espresso employs precise pressure and mind-blowing filter technology to create the coffee we love. But how exactly does it work? Espresso is created by forcing hot water at high pressure through finely ground coffee. The process is similar to making drip coffee, however the main difference lies in the pressure. The Head of the Group As the name suggests the group head is where you insert your portafilter when making espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure that results from the extraction. There are a variety of group heads each with its own advantages and disadvantages. Some focus on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. There are some that include a mix of features, like the E61 one, which is the classic choice among many baristas due to its ability to offer multiple benefits in one package. As you can see in the above image the group head is made up of several notches to place your portafilter and twist it with your hands to secure it. There is also a rubber gasket which is located inside the notches and helps create the seal when you insert your portafilter into the machine. The notches on the head allow for a precise placement of the portafilter, which is crucial for a consistent extraction. In addition to allowing you to easily place your portafilter in, the group head is also responsible for maintaining an even temperature. It does this by cycling hot water through the brew container and around the portafilter, ensuring that it is always at the correct temperature for extraction. This is crucial, since even a small difference in temperature can make the difference between a good and great espresso. The Pump Contrary to manual piston machines which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure necessary for espresso extraction. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger before it is shot through the ground coffee inside the group head. Pumps tend to be less expensive than piston-driven machines and tend to last longer. However, both types of machines can be damaged by excessive use and inadequate cleaning. They also add mechanical complexity, which can result in a high price tag on even the simplest models. Some espresso machines remove the pump completely and use steam pressure to brew espresso. The drawback of this is that the same boiler that produces steam also raises the temperature of the water to boiling which could lead to excessive extraction. In addition these machines typically have to restore their pressure between cups, which takes time and energy. Many espresso machines use a rotary or vibration pump. A vibration model makes use of a rotating disk to generate pressure, while a rotary model pushes hot water through the ground at high speed. Both types of machines can produce an excellent espresso, but rotary machines are quieter and more durable than vibration pumps. The Boiler The boiler is what makes the water warm to the ideal temperature to extract. The steam that is produced reaches the portafilter, which contains the espresso coffee grounds. espresso coffee machine is then channeled into the cup. During this process the steam causes enough pressure to push the grounds of the coffee through. This results in a layer crema that is then poured over. This is one of the hallmarks of a great espresso. There are three kinds of espresso machines, each with distinct pumps and the temperature of the brew. There are also different ways in which the brew could be controlled and the size of the cup that the machine can produce. The first espresso machines were steam-type. The earliest espresso machines were steam types. The coffee tasted bitter and burnt. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni. The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they imagine these machines. With a semi-automatic machine you have to grind the beans and then tamp them by hand. The pump is able to regulate the flow of water and pressure. This is a great compromise between the human touch and mechanized quality. The Filter Typically, espresso machines have filters that separate the grounds of the coffee as they go through the hot water. The filter is also an essential component of the temperature control system, as it keeps the machine from overheating. Filters also aid in flavor since it allows for the beans to flower for a longer period of time. This allows the beans to let their nuances out, and improves extraction. It is important to keep in mind that even the finest filter can result in a bad cup of coffee. The quality of the beans as well as the extraction, are still crucial. It's in this area that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you place the portafilter – the thingy that you put the coffee grounds into, when making espresso. In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. Steam then pushes the hot water through the grounds under high pressure. These types of machines are typically less expensive and simpler to maintain than pump-driven models. They are however limited to create the perfect brewing conditions as 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 utilize an air compressor to force hot water through grounds and are much more portable than electric steam-driven machines.