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How Does Machine Espresso Work? The machine espresso makes use of precise pressure, as well as a filtering technology that is amazing to make the coffee you love. What exactly is it that makes it work? To make an espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure. The Group Head The group head is the portafilter that you insert when brewing espresso. It disperses the water into the portafilter and regulates the pressure of the extraction. There are a variety of group heads each with their own advantages and disadvantages. Some are designed for stability of temperature while others are designed to handle pre-infusion. Others are built to control the lever. Some have a combination, such as the E61. This is a preferred choice for baristas since it provides multiple advantages in one package. As you can see from the image above, the group head is fitted with several notches. It is possible to place your portafilter into these notches and turn the head around to secure it. There is also a rubber gasket in the notches to help create an airtight seal when you insert your portafilter into the machine. The notches allow for an exact placement of the portafilter. This is essential for an even extraction. Aside from allowing you to effortlessly insert your portafilter the group head is responsible for maintaining an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is always at the right level for extraction. This is important because even a small difference in temperature can be the difference between a good and great espresso. The Pump In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to supply the nine atmospheric bars of pressure necessary to extract espresso. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee. Pumps are generally cheaper and last longer than piston-driven machines. However, both types of machines can deteriorate because of excessive use and poor cleaning. They also increase the complexity of mechanical systems that can lead to an expensive price for even the simplest models. Certain espresso machines utilize steam pressure instead of a pump in order to brew espresso. The downside is that the same boiler that produces steam also increases the temperature of the water to boiling and can result in excessive extraction. In addition the machines often have to rebuild their pressure between cups, which requires time and energy. A majority of espresso machines use the rotary or vibration pump, with a vibrating model that uses a vibrating disc to generate the pressure and a rotary model pushing hot water through the grounds under high speed. Both models can produce an excellent espresso, however Rotary machines are quieter and more durable than vibration pumps. The Boiler The boiler is the part that heats water to the optimal temperature for extraction. The resulting steam reaches the portafilter which holds ground espresso beans and is then pumped into the cup. The steam causes pressure to push through the coffee grounds. This results in a layer crema that is then poured over. This is a hallmark of a good espresso. There are three types of espresso makers, which differ in the type of pump they use and how hot the brew is. There are a variety of ways in which the brew can be controlled as well as the size of the cup the machine is capable of making. The first espresso machines were steam-type. They used a single boiler to make steam and brew, but the pressure they could produce was very low – just two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni. The most commonly used espresso maker is a semi-automatic machine that has an electric pump. These are the images people have when they imagine an espresso machine. If you have a semi-automatic machine you need to grind the beans and then tamp them by hand, but the pump regulates the flow of water and pressure. This is a perfect solution that combines human control with mechanized consistency. The Filter Typically, espresso machines use a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also a vital component of the temperature control system, as it keeps the machine from overheating. It also helps with flavor, as it allows for a longer bloom phase. My Home Page lets the beans release their flavor and allows for a better extraction. It is important to remember that even the finest filter can make a bad cup of coffee. The quality of the beans and the extraction, remain vital. It's here that the magic takes place. This is what makes espresso taste so delicious. The grouphead (also known as the brewhead) is where you put the portafilter, the device which you put the coffee grounds into, when making espresso. Steam-driven espresso machines use hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through coffee grounds under high pressure. These types of machines are typically less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to provide the ideal brewing conditions, as they only operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars. In recent years, espresso machines driven by a compressed air compressor have become increasingly popular. They utilize an air compressor to push hot water through grounds and are significantly more portable than steam-driven electric machines.