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How Does Machine Espresso Work? Machine espresso makes use of precise pressure and mind-blowing filter technology to create the coffee we love. What exactly is it? Espresso is made by forcing hot water under pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure. The Head of the Group The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. Some come with a combination of both, such as the E61. This is a preferred choice for baristas due to the fact that it has multiple advantages in one package. As you can see in the image above the group head is equipped with several notches. You place your portafilter in these notches, then twist the head to secure it. There is also a gasket of rubber in the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches on the head permit a precise location of the portafilter which is vital to ensure an even extraction. Aside from allowing you to effortlessly insert your portafilter the group head is also responsible for maintaining a consistent temperature. It does this by cycling hot water through the brew container and around the portafilter to ensure that it's always at the right temperature to extract. This is crucial, since even a small difference in temperature can make the difference between a good and great espresso. The Pump The motorized pumps in rotary espresso machines provide the nine atmospheric bars of pressure required to extract espresso. This differs from manual piston machines that use a lever. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee. Pumps are typically less expensive than piston-driven machines and tend to last longer, although both types of machine can get damaged through overuse and lack of cleaning. They also increase the complexity of mechanical systems which can result in the cost of even the simplest models. Certain espresso machines eliminate the pump entirely and utilize steam pressure to make espresso. The drawback of this is that the same boiler that produces steam also raises the temperature of the water until it reaches boiling and can result in excessive extraction. They also have to constantly rebuild their pressure in between cups. This takes energy and time. Many espresso machines make use of an rotary or a vibration pump. A vibration model employs a vibrating disk to generate pressure, while the circular model pushes hot liquid through the ground at a rapid speed. Both machines can make great espresso however rotary machines tend to be more quiet, durable and less likely to break down. The Boiler The boiler is the element that heats the water to the ideal temperature for extraction. espresso maker barista resulting steam is then transferred to the portafilter that contains ground espresso beans and is then funneled down into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This creates a crema on the top of the espresso. This is a sign of a good espresso. There are three kinds of espresso makers, and they differ in the type of pump they use and how hot the espresso is. There are a variety of ways in which the brew could be controlled as well as the size of the cup the machine is capable of making. The first espresso machines were steam-based. They had one boiler to create both steam and brew but the pressure they could produce was very low – just two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine. The most common espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they picture these machines. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the flow of water and pressure. This is a fantastic combination of human control and mechanized consistency. The Filter Espresso machines typically have filters that separate the grounds of the coffee from the hot water. The filter is also an essential element of the machine's temperature control, since it helps to prevent overheating. It also aids in flavor, since a filter allows for a more prolonged bloom time. This allows the beans to release their flavors, and allows for better extraction. It is important to keep in mind that even the best filter can result in a bad cup of coffee. The quality of the beans and the extraction process, are still very important. This is where the magic happens. It's what makes an espresso really taste great. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you use to put the grounds of coffee into when making espresso. In a steam-driven espresso machine hot water is heated in an airtight tank to create steam. Steam is then pushed through the grounds with high pressure. These kinds of machines tend to be less expensive and simpler to maintain than pumps-driven models. However, they are not as efficient in their ability to create the ideal brewing conditions, as they only operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bars. In recent years, compressed air-driven espresso machines have become more popular. They use an air compressor to force hot water through the grounds and are much more portable than steam-driven electric machines.