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How Does visit my home page ? Machine espresso uses precision pressure and amazing filter technology to make the delicious coffee we enjoy. What exactly is it? Espresso is produced by pushing hot water under pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the main difference. The Head of the Group As the name suggests, the group head is where you place your portafilter while brewing espresso. It disperses water in the portafilter and regulates the pressure of the extraction. There are many different types of group heads each with their own advantages and drawbacks. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Some are designed to control the lever. There are some that include a mix of features, like the E61, which is the standard choice for many baristas for its ability to offer multiple perks in one package. As you can see in the above photo The group head features several notches where you place your portafilter and then twist it by hand to lock it in. A gasket made of rubber is placed inside the notches to help make a seal when you insert your portafilter. The notches on the head permit a precise placement of the portafilter, which is vital for an efficient extraction. In addition to allowing you to easily connect your portafilter, the group head is also responsible to maintain an even temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket to ensure the temperature is always right to extract the coffee. It is important to realize that even a slight deviation can make the difference between a decent and a excellent espresso. The Pump In contrast to manual piston machines which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure needed 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 they tend to last longer, however both types of machines can become damaged due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which can increase the price of even the simpler models. Some espresso machines employ steam pressure instead of a pump in order to brew espresso. The disadvantage of this is that the boiler that produces steam also raises the temperature of the water to boiling which could lead to excessive extraction. In addition, these machines frequently have to restore their pressure between cups, which requires time and energy. Many espresso machines make use of a vibration or rotary pump, with a vibrating model using a rotating disc to create pressure, and rotating models that push hot water through the grounds under high speed. Both types of machine are capable of producing excellent espresso, however the rotary models are quieter and more durable than vibration pumps. The Boiler The boiler is the one that is used to heat the water to the perfect temperature for extraction. The steam that is created reaches the portafilter, which is the container that holds the espresso coffee grounds. It is then pumped into the cup. During this process the steam creates enough pressure to push the grounds of the coffee through. This creates a foam on top of the espresso. This is a sign of a good espresso. There are three types of espresso makers, and they differ in the type of pump they use and how hot the coffee is. There are different ways in which the brew can be controlled and the size of the cup the machine is capable of making. The first espresso machines were steam-type. They used one boiler to make steam and brew, however, the pressure they could produce was not very high – two bars of atmospheric pressure maximum. This led to the coffee tasting bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine. The most commonly used espresso machine is a semiautomatic model with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic machine you must grind the beans and tamp them by hand. However, the pump regulates the flow of water and pressure. This is a perfect combination of human control and mechanised consistency. The Filter Espresso machines typically have a filter that separates the grounds of coffee from hot water. The filter is also an essential part of the machine's temperature control, as it helps prevent overheating. It also enhances flavor, as a filter can allow for a longer bloom phase. This lets the beans release their flavors, and allows for better extraction. However it is crucial to remember that even a top filter can make a terrible cup of coffee, because the quality of the beans and extraction are important. It's here that the magic happens. This is the reason why espresso tastes so good. The grouphead, often called the brew head, is where the portafilter (the container you place the coffee ground into) sits when you're making espresso. In the steam-driven espresso machine hot water is heated in an airtight tank to create steam. This then pushes the hot water through the grounds at high pressure. These kinds of machines are usually cheaper and easier to maintain than pumps-driven models. However, they are limited in their ability to provide the perfect brewing conditions because they operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bars. In recent years, espresso machines driven by compressed air-pump have become increasingly popular. They use an air compressor to force the hot water through the grounds, and are far more portable than steam-driven electric machines.