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How Does Machine Espresso Work? Machine espresso makes use of precise pressure and incredible filter technology to produce the coffee we love. How exactly does it work? Espresso is made by pushing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee, but the difference is in the pressure. The Head of the Group The group head is the portafilter that you put in when making espresso. It is responsible for dispersing water into the portafilter before controlling the pressure that results from the extraction. There are many different kinds of group heads, each with their particular advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. There are some that include a mix of features, such as the E61 one, which is the classic choice among many baristas because of its ability to offer multiple benefits in one package. As you can see in the photo above the group head is equipped with several notches. The portafilter is placed in these notches and then twist the head to secure it. There is also a rubber gasket which is located inside the notches to help create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for a precise position of the portafilter which is vital for a consistent extraction. In addition to allowing you effortlessly insert your portafilter the group head is responsible to maintain an even temperature. coffee machine espresso does this by cycling hot water through the brew basket and around the portafilter to ensure that it is always at the correct temperature for extraction. This is vital, because even a few degrees can be the difference between a good and excellent espresso. The Pump Contrary to manual piston machines which use a lever to pressurize water, rotary espresso machines rely on motorized pumps to provide 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 prior to being shot through the ground coffee inside the group head. Pumps tend to be more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and insufficient cleaning. They also create mechanical complexity, which can result in an expensive price for even the simplest models. Some espresso machines eliminate the pump completely and employ steam pressure to create espresso. This can lead to over-extraction as the boiler that produces steam also heats the water to boil. Additionally, these machines frequently have to rebuild their pressure between cups, which requires time and energy. A majority of espresso machines use either a rotary or vibration pump, with a vibration model that uses a vibrating disc to generate the pressure, and the rotary model pushing hot water through the grounds under high speed. Both machines can produce excellent espresso, but rotary machines are more stable, quieter and less likely to fail. The Boiler The boiler is the part that heats the water to the optimal temperature for extraction. The steam that is produced reaches the portafilter that contains ground espresso beans and gets funnelled down into the cup. During this process, steam creates pressure to push through the coffee grounds. This creates a layer crema that is then poured over. This is the hallmark of a great espresso. There are three kinds of espresso machines, each having different pumps and brew temperature. There are also different ways in which the brew could be controlled as well as the dimensions of the cup the machine can make. The first espresso machines were steam-type. They employed one boiler to make steam and brew, however, the pressure they could generate was low – only two bars of atmospheric pressure, at most. This led to the coffee tasting bitter and burnt. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni. The most commonly used espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic espresso machine, you grind the beans and then tamp them by hand. However, the pump controls the flow of water and pressure. This is an excellent combination of human control and mechanized accuracy. The Filter Espresso machines usually use filters that separate the grounds of coffee from hot water. The filter is also an important part of the temperature control system as it keeps the machine from overheating. It also aids in flavor as a filter allows for a more prolonged bloom time. This helps the beans release their flavors and provides an opportunity for better extraction. However, it is important to keep in mind that even a great filter can make a terrible cup of coffee, because the quality of the beans and extraction is still essential. It's in this area that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead (also known as the brewhead) is where you put the portafilter, which is the thingy which you put the coffee grounds into, while making espresso. Steam-driven espresso machines use hot water that is heated in an airtight container to create steam. The steam then pushes hot water through coffee grounds under high pressure. These kinds of machines are generally cheaper and easier to maintain than pumps-driven models. They are however limited in their ability to create the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars. In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They utilize an air compressor to push hot water across the ground and are more mobile than electric steam-driven espresso machines.