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How Does Machine Espresso Work? Machine espresso employs precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly does it work? In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference. The Head of the Group The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure that results from the extraction. There are many different kinds of group heads each with its distinct advantages and drawbacks. Some focus on temperature stability, while others on pre-infusion features, and others are designed to control the lever. Some come with a combination of both, like the E61. espresso coffee machine is a favorite among baristas because it offers multiple advantages in one package. As you can see from the above photo the group head is fitted with a variety of notches. It is possible to place your portafilter inside these notches, and then twist the head to secure it. A gasket made of rubber is placed in the notches to create a seal when you insert your portafilter. The notches on the head permit an exact location of the portafilter which is crucial for a consistent extraction. In addition to allowing you easily insert your portafilter, the group head is responsible for maintaining a consistent temperature. This is accomplished by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is always at the right level to extract the coffee. This is crucial, since even a few degrees can be the difference between a good and great espresso. The Pump In contrast to manual piston machines which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger prior being pumped through the ground coffee in the group head. Pumps tend to be cheaper and last longer than piston-driven machines. However, both kinds of machines can deteriorate because of excessive use and inadequate cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simplest models. Some espresso machines use steam pressure instead of a pump in order to brew espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of the water to the point of boiling and can result in excessive extraction. In addition, these machines frequently have to rebuild their pressure between cups, which requires time and energy. Many espresso machines make use of an rotary or vibrating pump, which is a vibration model using a rotating disc to create pressure, and the rotary model pushing hot water through the grounds under high speed. Both machines can make excellent espresso but rotary machines are more quiet, durable and less likely to fail. The Boiler The boiler is the one that is used to heat the water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter which holds the ground espresso and gets funnelled down into the cup. The steam generates enough pressure to push the grounds of the coffee through. This produces a layer of crema on top. This is a hallmark of a great espresso. There are three types of espresso makers, and they differ in the kind of pump they use and how hot the coffee is. There are different ways in which the brew could be controlled as well as the size of the cup the machine can make. The first espresso machines were steam-types. They had one boiler to create both steam and brew however the pressure they were able to produce was not very high – two bars of atmospheric pressure, at most. This led to the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni. The most common espresso machine is a semiautomatic with an electric pump. This is what people envision when they think of an espresso machine. If you have a semi-automatic machine you need to grind the beans and then tamp them by hand. The pump is able to regulate the flow of water and pressure. This is an excellent compromise between human control and mechanized reliability. 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 important element of the temperature control system, as it prevents the machine from overheating. A filter also helps with flavor, as it permits a longer flowering period. This lets the beans let their nuances out, and improves extraction. However, it is important to keep in mind that even a high-quality filter could result in a bad cup of coffee, because the quality of the beans and extraction is essential. It's here 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, which is the thingy that you put the coffee grounds in, when making espresso. In an espresso machine that is driven by steam, hot water is heated in an airtight container to produce steam, which then pushes the hot water through the grounds under high pressure. These kinds of machines tend to be less expensive and easier to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing, as they 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 use an air-compressor to force hot water into the ground, and are more mobile than electric steam-driven espresso machines.