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How Does Machine Espresso Work? The machine espresso uses precision pressure, and a filtering technology that is amazing to make the coffee you enjoy. What exactly is it? To make espresso hot water is pushed under 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 The group head is the portafilter that you insert when brewing espresso. It distributes water into the portafilter, and then controls the pressure of the extraction. There are several different types of group heads, each with their own advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion capabilities, while others are designed to control the lever. Some include a mix of features, such as the E61, which is considered the standard choice for many baristas because of its ability to provide multiple benefits in one package. As you can see from the image above the group head is equipped with several notches. It is possible to place your portafilter inside these notches, and then twist the head to lock it. A rubber gasket is located within the notches to create a seal as you insert your portafilter. The notches permit precise placement of your portafilter. This is essential for a consistent extraction. The group head not only lets you to insert your portafilter easily, but it also maintains a constant temperature. It does this by circulating hot water through the brew container and around the portafilter, making sure that it is always at the right temperature for extraction. It is important to realize that even a slight deviation can make the difference between a good and excellent espresso. The Pump Unlike manual piston machines, which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to provide the nine atmospheric bars of pressure required for espresso extraction. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee. Pumps tend to be cheaper than piston-driven machines and tend to last longer, although both types of machines could degrade with overuse and insufficient cleaning. They also create mechanical complexity that can lead to a high price tag on even the most basic models. Some espresso machines make use of steam pressure instead of a pump to brew espresso. This can result in over-extraction because the boiler that produces steam also heats the water to boil. In addition these machines are often required to rebuild their pressure between cups, which takes time and energy. Many espresso machines use either a vibration or rotary pump. A vibration model uses an oscillating disk to create pressure, while a rotary model pushes hot water through the ground at high speed. Both models can make excellent espresso, but rotary machines are quieter and more durable than vibration pumps. The Boiler The boiler is what heats the water to the perfect temperature to extract. The steam created reaches the portafilter, which contains the espresso coffee grounds. It is then pumped into the cup. The steam causes enough pressure to push the grounds of coffee through. This produces a layer of crema on top. This is one of the main characteristics of a good espresso. There are three distinct types of espresso machines, each with different types of pumps and brew temperature. There are different ways to control the amount of brew, as well as the size of cup that can be produced by the machine. The earliest espresso machines were steam-based. The first espresso machines were steam types. This resulted in the coffee tasting bitter and burnt. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine. The most popular espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic machine, you must grind the beans and then tamp them by hand. However, the pump regulates the flow of water and pressure. This is a great compromise between the human touch and mechanized consistency. The Filter Typically, espresso machines employ filters to separate the grounds of the coffee as they go through the hot water. The filter is also an important part of the temperature control system because it stops the machine from overheating. A filter can also help with flavor, as it permits an extended flowering time. This helps the beans to release their nuances and gives an opportunity for a better extraction. However, it is important to remember that even a great filter can result in a poor cup of coffee, since the quality of the beans and extraction is crucial. This is where the magic happens, it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you place the portafilter, the thingy that you put the grounds of your coffee into when making espresso. In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds with high pressure. They are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited in their ability 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, espresso machines driven by a compressed air pump have become increasingly popular. They use an air compressor to force the hot water through the grounds and are much more portable than steam-driven electric machines.