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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? In order to make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure. The Group Head The name implies the group head is where you place your portafilter while brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are a variety of types of group head, each with their particular advantages and drawbacks. Some are designed to provide temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. There are some that come with a range of features, like the E61, which is the classic choice among many baristas because of its ability to offer multiple perks in one package. As you can see in the photo above, the group head has several notches where you place your portafilter before twisting it manually to secure it. A gasket made of rubber is placed within the notches to create a seal as you insert your portafilter. The notches on the head permit a precise positioning of the portafilter which is vital for a consistent extraction. The group head is not just able to allow the portafilter to be inserted easily, but it also maintains the temperature at a constant level. It does this by circulating 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 small difference in temperature can mean the difference between excellent and great espresso. The Pump Unlike manual piston machines, that use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure required to extract espresso. This pressure is built up 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 may degrade because of excessive use and insufficient cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simplest models. Some espresso machines employ steam pressure instead of a pump in order to brew espresso. The downside is that the boiler that produces steam also increases the temperature of water to boiling which can cause over-extraction. The machines must also constantly rebuild their pressure in between cups. This takes energy and time. A majority of espresso machines utilize an rotary or a vibration pump. A vibration model employs a rotating disk to generate pressure, whereas a rotary model pushes hot water through the ground at a rapid speed. Both machines can produce excellent espresso but rotary machines are quieter, more durable and less likely to break. The Boiler The boiler is the part that heats water to the optimal temperature to extract. The steam that is created gets to the portafilter which is a container for espresso grounds. The steam is then channeled into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This creates a layer crema that is then poured over. This is a hallmark of a good espresso. There are three distinct types of espresso machines, each having different pumps and brew temperature. There are also different ways that the brew can be controlled, as well as the size of the cup the maker can create. The earliest espresso machines were steam type. Coffeee UK were steam types. This led to the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni. The most common espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans by yourself while the pump controls the flow of water and pressure. This is a great compromise between human control and mechanized consistency. The Filter Espresso machines usually use a filter that separates the grounds of the coffee from the hot water. The filter is also an essential element of the machine's temperature control, as it prevents overheating. A filter also improves flavor as it allows for a longer flowering period. This allows the beans to release their flavors, and improves extraction. However it is crucial to remember that even a great filter can make a terrible cup of coffee as the quality of the beans and extraction is still vital. It's here that the magic happens. This is what makes espresso taste so delicious. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you use to put the coffee grounds in, when making espresso. In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam, which is then pushed through the grounds with high pressure. These types of machines are usually cheaper and easier to maintain than pump-driven models. They are however limited 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 use an air compressor to push hot water into the grounds and are more portable than steam-driven electric machines.