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How Does Machine Espresso Work? Machine espresso employs precise pressure and amazing filter technology to make the perfect cup of coffee. What exactly does it work? To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the main difference. The Group Head The group head is the portafilter is inserted when you are making espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure that results from the extraction. There are various kinds of group head, each with their particular advantages and disadvantages. Some are specifically designed for temperature stability while others are designed to handle pre-infusion. Others are made to control the lever. There are also some that contain a variety of features, like the E61 one, which is the most popular choice among baristas due to its ability to offer multiple perks in one package. As you can see from the image above the head of the group has a number of notches. You can place your portafilter in these notches and then turn the head around to secure it. There is also a rubber gasket in the notches and helps create the seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is crucial for a consistent extraction. In addition to allowing you easily insert your portafilter, the group head is also responsible for maintaining an even temperature. It does this by circulating hot water through the brew pan and around the portafilter to ensure that it's always at the correct temperature to extract. This is important, as even a few degrees can mean the difference between good and great espresso. The Pump Contrary to manual piston machines that use a lever to pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure required for espresso extraction. The pressure is created by pumping water through a heat exchanger and then through the ground coffee. Pumps tend to be less expensive than piston-driven machines, and tend to last longer. However, both types of machines may get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, and can add to prices of even simplest models. Certain espresso machines can eliminate the pump completely and make use of steam pressure to make espresso. This can cause over-extraction because the boiler that makes steam also heats the water until it comes to a boil. In addition these machines typically have to rebuild their pressure between cups, which requires time and energy. Many espresso machines make use of either a vibration or rotary pump. A vibration model uses a rotating disk to generate pressure, whereas a rotating model pushes hot water through the ground at high speed. Both machines can make great espresso, but rotary machines are more stable, quieter and less likely to break. The Boiler The boiler is the element which heats the water to the ideal temperature to extract. The steam that is produced will eventually reach the portafilter, which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process the steam generates enough pressure to push the coffee grounds through. This results in a crema on top of the espresso. This is one of the hallmarks of a good espresso. There are three types of espresso machines, each with different pumps and brew temperature. There are also different ways in which the brew could be controlled and the size of the cup the machine can produce. The first espresso machines were steam-types. They employed a single boiler to make both brew and steam, however the pressure they were able to generate was low – only two bars of atmospheric pressure at the most. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni. The most popular espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they picture these machines. With read here -automatic espresso machine, you grind the beans and tamp them yourself but the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanised accuracy. The Filter Espresso machines typically have filters that separate the coffee grounds from the hot water. The filter is also an essential element of the machine's temperature control, as it helps prevent overheating. It also improves flavor, since a filter lets you enjoy a longer bloom phase. This allows the beans to release their nuances, and allows for a better extraction. It is important to remember that even the best filter could result in a poor cup of coffee. The quality of the beans, and the extraction process, remain vital. It's in this area that the magic takes place. This is the reason why espresso tastes so good. The grouphead (also known as the brewhead) is where you put the portafilter – the thingy that you put the grounds of coffee into when making espresso. Steam-driven espresso machines make use of hot water that is heated inside an airtight container to create steam. The steam then pushes hot water through the grounds of coffee under high pressure. These kinds of machines are usually less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to produce the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar. In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to force hot water into the grounds and are significantly more portable than electric steam-driven machines.