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How Does Machine Espresso Work? Machine espresso utilizes precise pressure and incredible filter technology to produce the coffee we love. 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 making drip coffee. However, the pressure is the primary difference. The Head of the Group The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing water into the portafilter and then controlling the pressure that results from the extraction. There are many different types of group heads each with their own advantages and disadvantages. Some focus on temperature stability, some on pre-infusion features, and others are designed to control the lever. Some include a combination such as the E61. This is a very popular choice for baristas as it provides a variety of advantages in one package. As you can see in the image above the group head comes with numerous notches that you can put your portafilter, then twist it with your hands to lock it in. A rubber gasket is located inside the notches, which helps create a seal while you insert your portafilter. The notches on the head permit an exact position of the portafilter which is necessary for an efficient extraction. Aside from allowing you to effortlessly insert your portafilter the group head is also responsible to ensure that the temperature remains even. This is done by cycling hot water around the portafilter and through the brew-basket to ensure the temperature is always right to extract the coffee. This is important, as even a few degrees can make the difference between a good and excellent espresso. The Pump In contrast to piston machines that are manually operated, that use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure needed to extract espresso. The pressure builds 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 than piston-driven machines, and tend to last longer, however both types of machines may degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, which could increase the cost of even the simpler models. Some espresso machines employ steam pressure instead of a pump in order to brew espresso. This can cause over-extraction because the boiler that produces steam also causes the water to boil. In addition these machines are often required to rebuild their pressure between cups, which requires time and energy. Many espresso machines use the rotary or vibration pump. A vibration model makes use of a vibrating disk to generate pressure, while a rotary model pushes hot water through the ground at high speed. Both machines produce great espresso however rotary machines tend to be more stable, quieter and less likely to break down. The Boiler The boiler is the part that heats water to an ideal temperature for extraction. The resulting steam reaches the portafilter that contains the ground espresso and is then funneled down into the cup. During this process, the steam causes pressure to push through the coffee grounds. This results in a crema on the top of the espresso. This is the hallmark of a good espresso. There are three kinds of espresso makers. They differ in the kind of pump they use and how hot the coffee is. There are various ways that the brew can be controlled and the size of the cup that the machine can produce. The first espresso machines were steam type. The first espresso machine s were steam types. The coffee tasted bitter and burned. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni. The most popular espresso maker is a semi-automatic machine 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. The pump controls the flow of water and pressure. This is a perfect compromise between human control and mechanised consistency. The Filter Espresso machines usually use filters that separate the grounds of the coffee from the hot water. The filter is also a crucial element of the temperature control system, because it stops the machine from overheating. It also aids in flavor, since a filter allows for a longer bloom phase. This helps the beans release their nuances and gives an opportunity for a better extraction. However, it is important to keep in mind that even a good filter can make a terrible cup of coffee, since the quality of the beans and extraction are crucial. It's in this area that the magic takes place. This is what makes espresso taste so delicious. The grouphead, sometimes called the brewhead, is where the portafilter (the thingy you put the coffee grounds into) sits when you're making espresso. Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then moves hot water through the grounds of coffee under high pressure. These types of machines tend to be cheaper and easier to maintain than pump-driven models. They are however limited 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, compressed air-pump-driven espresso machines have been gaining popularity. They make use of an air compressor to push hot water through the ground and are much more mobile than steam-driven electric espresso machines.