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How Does Machine Espresso Work? Machine espresso utilizes precise pressure and incredible filter technology to produce the delicious coffee we enjoy. What exactly is it? To make an espresso, hot water is forced under high pressure through finely ground coffee. compact espresso machine is similar to that of making drip coffee. However the pressure is the primary difference. The Group Head As the name suggests, the group head is where you place your portafilter while making espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are a variety of types of group head, each with their own advantages and drawbacks. Some are focused on temperature stability, others on pre-infusion features, and others are designed to control the lever. Some have a combination, such as the E61. This is a very popular choice for baristas because it offers multiple benefits in a single package. As you can see from the above photo the head of the group is fitted with several notches. You can place your portafilter into these notches and twist the head to secure it. A gasket made of rubber is placed within the notches to create a seal when you insert your portafilter. The notches allow for an exact placement of the portafilter. This is crucial for a consistent extraction. The group head is not just able to allow you to place your portafilter easily, but it also maintains an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it is always at the right temperature to extract. This is important, as even a few degrees can make the difference between good and excellent espresso. The Pump The motorized pumps that are used in rotary espresso machines provide the nine atmospheric bar pressure required to extract espresso. This is different from manual piston machines which use a lever. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee. Pumps are typically cheaper and last longer than piston-driven machines. However, both types of machines may degrade due to excessive use and poor cleaning. They also make mechanically complex, which can result in costly prices for even the simplest models. Some espresso machines use steam pressure instead of a pump to brew espresso. The downside is that the boiler that produces steam also increases the temperature of water to the point of boiling and can result in over-extraction. The machines must also constantly rebuild their pressure between cups. This takes energy and time. A majority of espresso machines utilize the rotary or vibration pump. A vibration model utilizes an oscillating disk to create pressure, whereas a rotary model pushes hot water through the ground at a fast speed. Both machines produce great espresso, but rotary machines are quieter, more durable and less likely to break down. The Boiler The boiler is what will heat the water to the ideal temperature for extraction. The resulting steam reaches the portafilter that contains ground espresso beans and is then funneled down into the cup. During this process the steam is able to create enough pressure to push the coffee grounds through. This results in a whipped-up the top of the espresso. This is a hallmark of a great espresso. There are three kinds of espresso makers, and they differ in the kind of pump they use and how hot the espresso is. There are different ways to control the strength of the brew and the size of the cup that can be made by the machine. The first espresso machines were steam-type. The first espresso machines were steam types. The coffee tasted bitter and burned. This is why the Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine. The most common espresso machine is a semiautomatic with 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 yourself but the pump controls the flow of water and pressure. This is a great compromise between the human touch and mechanized consistency. The Filter Typically, espresso machines have filters to separate the grounds of the coffee as they go through the hot water. The filter is also an important component of the temperature control system as it prevents the machine from overheating. It also enhances flavor as a filter allows for a more prolonged bloom phase. This helps the beans release their flavors and provides an opportunity for better extraction. However it is crucial to remember that even a great filter can result in a poor cup of coffee, because the quality of the beans and extraction is vital. This is where the magic happens, it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you put the portafilter – the thingy which you put the coffee grounds in, when making espresso. In the steam-driven espresso machine hot water is heated in an airtight tank to create steam. This is then pushed through the grounds under high pressure. These kinds of machines tend to be less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their capacity to create the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar. In recent years, compressed-air-pump-driven espresso machines have become more popular. They use an air compressor to force hot water through the grounds, and are far more portable than electric steam-driven machines.