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How Does Machine Espresso Work? The machine espresso makes use of precise pressure and filter technology that is awe-inspiring to create the coffee you enjoy. What exactly is it that makes it work? To make an espresso hot water is forced under high pressure through finely ground coffee. best portable espresso makers is similar to making drip coffee but the key difference is in the pressure. The Head of the Group The name implies the group head is the place you place your portafilter when brewing espresso. It disperses water into the portafilter, and then controls the pressure of the extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are specifically designed for temperature stability while others are specifically designed to handle pre-infusion. Some are designed to control the lever. There are even some that come with a range of features, such as the E61, which is considered to be the most popular among baristas due to its ability to offer multiple perks in one package. As you can see in the above photo the group head has a number of notches. The portafilter is placed in these notches, then twist the head to lock it. A gasket of rubber is situated in the notches to create a seal while you insert your portafilter. The notches permit the precise placement of the portafilter. This is crucial to ensure a consistent extraction. The group head does not just allow you to put in your portafilter easily, but it also maintains the same temperature. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it's always at the correct temperature to extract. It is important to remember that even a small variation can mean the difference between a good and great espresso. The Pump The motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure needed to extract espresso. This is different from manual piston machines which use levers. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head. Pumps are generally less expensive than piston-driven machines, and tend to last longer, however both types of machines can become damaged due to excessive use and poor cleaning. They also add mechanical complexity and can lead to an expensive price for even the most basic models. Some espresso machines remove the pump completely and instead utilize steam pressure to make espresso. The downside is that the same boiler that produces steam also raises the temperature of the water until it reaches boiling which could lead to excessive extraction. They also have to constantly rebuild their pressure in between cups. This takes energy and time. A large majority of espresso machines employ either a vibration or rotary pump. A vibration model makes use of a vibrating disk to generate pressure, while a Rotary model pushes hot coffee through the ground at a high speed. Both machines can make great espresso, but rotary machines are more quiet, durable and less likely to fail. The Boiler The boiler is the element that heats water to the optimal temperature to extract. The steam that is produced reaches the portafilter containing ground espresso beans and is then pumped into the cup. In this process, the steam creates pressure that pushes through the grounds of the coffee. This results in a whipped-up top of the espresso. This is a sign of a good espresso. There are three types of espresso makers, which differ in the type of pump they employ and how hot the espresso is. There are also different ways that the brew can be controlled, as well as the dimensions of the cup the machine is capable of making. The first espresso machines were steam-types. The earliest espresso machines were steam types. This led to the coffee tasting burnt and bitter. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine. The most commonly used espresso machine is a semiautomatic one with an electric pump. These are the things people think of when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans on your own, but the pump regulates the water flow and pressure. This is an excellent compromise between human touch and the mechanized accuracy. The Filter Typically, espresso machines use a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a vital component of the machine's temperature control, as it helps prevent overheating. It also aids in flavor as a filter can allow for a longer bloom time. This allows the beans to release their flavor and gives the chance for better extraction. However it is crucial to keep in mind that even a great filter could result in a bad cup of coffee, since the quality of the beans and extraction are vital. It's here that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you place the portafilter, the thingy used to place the grounds of your coffee into when making espresso. In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds under high pressure. These machines are less expensive and easier for the user to maintain than pumps-driven models. They are however limited in their ability 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, compressed air-pump-driven espresso machines have been gaining popularity. They make use of an air compressor to force hot water into the ground. They are also more mobile than electric steam-driven espresso machines.