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How Does Machine Espresso Work? Machine espresso makes use of precise pressure and incredible filter technology to produce the perfect cup of coffee. 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 major difference is in the pressure. The Head of the Group As the name implies the group head is the place you insert your portafilter when making espresso. It distributes water into the portafilter, and then controls the pressure of the extraction. There are many different kinds of group head, each with their unique advantages and disadvantages. Some focus on temperature stability, while others on pre-infusion features, and others are designed to control the lever. Some include a combination such as the E61. This is a favorite among baristas as it provides a variety of advantages in a single package. As you can see in the above image The group head features several notches to place your portafilter and then twist it manually to secure it. A rubber gasket is located inside the notches to help create a seal when you insert your portafilter. The notches on the head allow for a precise positioning of the portafilter which is vital to ensure an efficient extraction. Aside from allowing you to easily insert your portafilter, the group head is also responsible to maintain an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it's always at the correct temperature for extraction. This is important, as even a small difference in temperature can make the difference between good and great espresso. The Pump The motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure required for espresso extraction. This is different from manually operated piston machines that employ levers. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger prior to being pumped through the ground coffee in the group head. Pumps are generally less expensive than piston-driven machines and tend to last longer, but both types of machines can get damaged through overuse and lack of cleaning. They also increase the complexity of mechanical systems, which can result in an expensive price for even the most basic models. Certain espresso machines remove the pump completely and employ steam pressure to create espresso. The drawback of this is that the boiler that produces steam also increases the temperature of the water to the point of boiling and can result in excessive extraction. Additionally these machines are often required to rebuild their pressure between cups, which requires time and energy. Many espresso machines use either a vibration or rotary pump. A vibration model employs an oscillating disk to create pressure, while a rotary model pushes hot water through the ground at high speed. Both types of machines can make excellent espresso, but rotary machines are quieter and more durable than vibration pumps. The Boiler The boiler is the element that heats water to an ideal temperature for extraction. The steam produced will eventually reach the portafilter, which contains the espresso coffee grounds. The steam is then channeled into the cup. The steam causes enough pressure to push the grounds of coffee through. This results in a layer of crema on top. This is a hallmark of a great espresso. There are three types of espresso makers, which differ in the type of pump they employ and the degree of heat that 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 maker can create. The first espresso machines were steam-type. They had one boiler to make both steam and brew, however the pressure they were able to produce was not very high – two bars of atmospheric pressure, at most. This led to the coffee tasting burnt and bitter. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine. The most well-known espresso maker is a semiautomatic machine that has 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 The pump, however, regulates the water flow and pressure. This is a perfect combination of human control and mechanised reliability. The Filter Espresso machines usually have a filter that separates the coffee grounds from the hot water. The filter is also a vital part of the machine's temperature control, as it helps prevent overheating. A filter can also help with flavor since it allows for an extended flowering time. This lets the beans release their flavor and also allows for better extraction. It is important to keep in mind that even the best filter could result in a poor cup of coffee. The quality of the beans, and the extraction process, remain vital. This is where the magic happens. It's what makes an espresso really taste great. The grouphead, often called the brewhead, is where the portafilter (the device you put 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 container to create steam. Steam then pushes the hot water through the grounds with high pressure. These machines are less expensive and easier to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars. In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water through the ground. They are also more mobile than steam-driven electric espresso machines.