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How Does Machine Espresso Work? The machine espresso makes use of precise pressure, as well as a filtering system that is awe-inspiring to make the coffee you love. How exactly does it work? Espresso is created by forcing hot water under pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure. The Head of the Group As the name suggests, the group head is where you insert your portafilter when brewing espresso. It disperses the water into the portafilter and regulates the pressure of extraction. There are many different kinds of group head each with its own advantages and drawbacks. Some are designed for the stability of temperature while some are designed to handle pre-infusion. Some are designed to control the lever. Some include a combination like the E61. This is a favorite among baristas since it provides multiple advantages in one package. As you can see in the photo above, the group head is fitted with several notches. You can place your portafilter into these notches and twist the head to lock it. A gasket of rubber is situated inside the notches to help create a seal when you insert your portafilter. The notches allow for precise placement of the portafilter. This is essential for an efficient extraction. Aside from allowing you to easily connect your portafilter, the group head is responsible to ensure that the temperature remains even. This is accomplished by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is at the right level for extraction. It is important to note that even a slight deviation can make the difference between a good and excellent espresso. The Pump In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to supply the nine atmospheric bars of pressure required for espresso extraction. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pumped through the ground coffee inside the group head. Pumps tend to be cheaper than piston-driven machines and tend to last longer. However, both types of machines can degrade with overuse and insufficient cleaning. They also create mechanical complexity that can lead to costly prices for even the simplest models. Some espresso machines use steam pressure instead of a pump to make espresso. The drawback is that the boiler that produces steam also raises the temperature of the water to boiling, which can lead to excessive extraction. These machines also have to constantly rebuild their pressure in between cups. This takes energy and time. Many espresso machines make use of a rotary or vibration pump. A vibration model makes use of a vibrating disk to generate pressure, whereas the rotary model pushes hot water through the ground at a rapid speed. Both models can produce an excellent espresso, however the rotary models are quieter and more durable than vibration pumps. The Boiler The boiler makes the water warm to the ideal temperature for extraction. The steam that is created will eventually reach the portafilter, which is a container for espresso grounds. It is then poured into the cup. In this process, the steam creates pressure and pushes through the grounds of the coffee. This results in a layer of crema on top. This is a sign of a good espresso. There are three types of espresso machines, each having different types of pumps and brew temperature. There are a variety of ways in which the brew could be controlled as well as the dimensions of the cup the maker can create. The first espresso machines were steam-types. They employed one boiler to make steam and brew, however the pressure they were able to produce was very low – just two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. This is why the Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine. The most commonly used espresso maker is a semiautomatic machine that has an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is a great solution that combines human control with mechanized reliability. The Filter Typically, espresso machines have filters to separate the coffee grounds as they pass through the hot water. The filter is also an essential component of the machine's temperature control, since it stops overheating. A filter also helps with flavor, as it permits the beans to flower for a longer period of time. This allows the beans to release their flavor and also allows for better extraction. However it is crucial to remember that even a good filter can result in a poor cup of coffee, because the quality of the beans and extraction are essential. This is where the magic happens, and it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you place the portafilter, the thingy which you put the coffee grounds in, when making espresso. In the steam-driven espresso machine hot water is heated in an airtight tank to produce steam, which is then pushed through the grounds under high pressure. These kinds of machines are usually less expensive and easier to maintain than pump-driven models. They are however limited in their ability to create the perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars. In recent years, espresso machines powered by a compressed air compressor have become increasingly popular. They use an air compressor to push hot water through the ground and are more mobile than electric steam-driven espresso machines.