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How Does Machine Espresso Work? Machine espresso makes use of precise pressure and incredible filter technology to produce the delicious coffee we enjoy. What exactly is it that makes it work? In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure. The Head of the Group As the name implies the group head is the place you place your portafilter while brewing espresso. It distributes water into the portafilter, and regulates the pressure of the extraction. There are many different kinds of group heads, each with their distinct advantages and disadvantages. Some are focused on temperature stability, some on pre-infusion options, and others are designed to control the lever. Some include a combination like the E61. This is a favorite among baristas due to the fact that it has multiple advantages in a single 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 then twist it manually to lock it in. A gasket of rubber is situated within the notches to create a seal as you insert your portafilter. The notches permit precise placement of the portafilter. This is essential for a consistent extraction. The group head is not just able to allow you to place your portafilter easily however it also keeps a constant temperature. It does this by cycling hot water through the brew pan and around the portafilter to ensure that it's always at the right temperature to extract. This is important, as just a few degrees could mean the difference between good and great espresso. The Pump In contrast to manual piston machines which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure required to extract espresso. This pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger prior to being pumped through the ground coffee inside the group head. Pumps are generally less expensive than piston-driven models, and they tend to last longer, although both types of machines may become damaged due to excessive use and poor cleaning. They also add mechanical complexity that can lead to an expensive price for even the simplest models. espresso machine coffee do away with the pump completely and instead employ steam pressure to create espresso. The drawback of this is that the boiler that produces steam also increases the temperature of the water to boiling which could lead to excessive extraction. In addition these machines are often required to restore their pressure between cups, which takes time and energy. Many espresso machines use the rotary or vibration pump. A vibration model makes use of an oscillating disk to create pressure, while the circular model pushes hot liquid through the ground at a rapid speed. Both machines can make great espresso but rotary machines are more quiet, durable and less likely to break down. The Boiler The boiler is the component that heats water to the ideal temperature for extraction. The steam produced is then directed to the portafilter, which contains the espresso coffee grounds. It is then pumped into the cup. The steam is able to create enough pressure to push the coffee grounds through. This results in a crema on the top of the espresso. This is a sign of a good espresso. There are three distinct types of espresso machines, each with distinct pumps and the temperature of the brew. There are different ways to control the amount of brew, as well as the size of the cup that can be produced by the machine. The first espresso machines were steam-type. They utilized a single boiler to make both steam and brew, however the pressure they were able to produce was not very high – two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine. The most common espresso machine is a semiautomatic model with an electric pump. This is what people envision when they think of an espresso maker. If you have a semi-automatic machine you have to grind the beans and then tamp them by hand. However, the pump provides regulated water flow and pressure. This is a great compromise between the human touch and the mechanized accuracy. The Filter Typically, espresso machines employ filters that separate the coffee grounds as they pass through the hot water. The filter is also a vital component of the temperature control system as it keeps the machine from overheating. It also helps with flavor, since a filter lets you enjoy a longer bloom phase. This lets the beans release their nuances, and allows for better extraction. However, it is important to remember that even a top filter can make a terrible cup of coffee, as the quality of the beans and extraction are crucial. This is where the magic happens, and it's what makes espresso taste great. The grouphead (also called the brewhead) is where you put the portafilter, which is the thingy which you put the grounds of your coffee into when 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 into the grounds of coffee at high pressure. These machines are cheaper and easier to maintain than pumps-driven models. However, they are limited in their ability to create the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars. In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They use an air compressor to force hot water into the ground. They are also more mobile than electric steam-driven espresso machines.