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How Does Machine Espresso Work? Machine espresso utilizes precise pressure and amazing filter technology to make the perfect cup of coffee. How exactly does it work? Espresso is made by pushing 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 Group Head The group head is the portafilter you put in when making espresso. It disperses water in the portafilter, and controls the pressure of the extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are designed to provide temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. espresso machines uk contain a variety of features, such as the E61, which is considered the most popular choice among baristas because of its ability to offer multiple perks in a single package. As you can see from the photo above the group head is fitted with several notches. You can place your portafilter in these notches and then twist the head to lock it. A gasket of rubber is situated inside the notches to help create a seal while you insert your portafilter. The notches on the head allow for an exact position of the portafilter which is crucial to ensure a consistent extraction. In addition to allowing you easily place your portafilter in, the group head is also responsible for maintaining an even temperature. It does this by cycling hot water through the brew pan and around the portafilter to ensure that it is always at the right temperature to extract. This is important, as just a few degrees could be the difference between a good and excellent espresso. The Pump The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure required for espresso extraction. This is different from manual piston machines that use a lever. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee. Pumps are typically less expensive than piston-driven machines, and they tend to last longer. However, both types of machines can degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, which can raise the cost of even simple models. Some espresso machines eliminate the pump completely and make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that produces steam also causes the water to boil. In addition these machines typically have to rebuild their pressure between cups, which requires time and energy. Many espresso machines employ the rotary or vibration pump, which has a vibration model using a rotating disc to create pressure and the rotary model pushing hot water through the grounds at high speed. Both machines produce great espresso, however rotary machines are more quiet, durable and less likely to break down. The Boiler The boiler is the one that makes the water warm to a temperature that is ideal to extract. The resulting steam is then transferred to the portafilter that contains the ground espresso and is then pumped down into the cup. During this process, steam creates pressure and pushes through the grounds of the coffee. This results in a layer of crema that is then poured over. This is one of the main characteristics of a good espresso. There are three types of espresso makers. They differ in the type of pump they use and how hot the brew is. There are various ways to control the strength of the brew and the size of cup that can be produced by the machine. The earliest espresso machines were steam type. They employed only one boiler to make steam and brew, but the pressure they could create was minimal – two bars of atmospheric pressure at the most. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni. The most popular espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they imagine these machines. With a semi-automatic machine you need to grind the beans and then tamp them by hand, but the pump is able to regulate the flow of water and pressure. This is a great compromise between the human touch and the mechanized consistency. The Filter Espresso machines typically use a filter that separates the grounds of coffee from hot water. The filter is also a crucial part of the temperature control system, as it prevents the machine from overheating. It also aids in flavor, as it allows for a more prolonged bloom time. This allows the beans to release their flavors and provides an opportunity for a better extraction. However, it is important to keep in mind that even a top filter could result in a bad cup of coffee, since the quality of the beans and extraction are crucial. This is where the magic happens, and it's what makes an espresso really taste great. The grouphead, sometimes called the brewhead, is where the portafilter (the container you place the coffee ground into) is placed when making espresso. In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam. Steam is then pushed through the grounds under high pressure. These kinds of machines are generally cheaper and easier to maintain than pumps-driven models. They are however limited to create the perfect brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars. In recent years, espresso machines driven by a compressed air compressor have become increasingly popular. They use an air compressor to push hot water into the grounds and are more portable than steam-driven electric machines.