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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. How does it work exactly? Espresso is made by pushing 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 The group head is the portafilter you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are many different kinds of group heads each with its distinct advantages and disadvantages. Some are focused on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. There are even some that have a combination of features, such as the E61, which is to be the most popular among baristas because of its ability to provide multiple benefits in a single package. As you can see from the image above the head of the group is fitted with a variety of notches. You can place your portafilter into these notches and twist the head to lock it. A gasket made of rubber is placed inside the notches to help create a seal while you insert your portafilter. The notches allow for an exact placement of the portafilter. This is essential for an even extraction. Apart from allowing you easily connect your portafilter, the group head is also responsible for maintaining a consistent temperature. This is done by cycling hot water around the portafilter, and through the brew basin, ensuring the temperature is always right for extraction. This is vital, because just a few degrees could make the difference between a good and great espresso. The Pump The motorized pumps in espresso machines that rotate provide the nine atmospheric bars of pressure required to extract espresso. This is different from manual piston machines that use a lever. The pressure is created by removing tap water from a reservoir, and pumping it through a heat exchanger before being shot through the ground coffee inside the group head. Pumps are generally more affordable and last longer than piston-driven machines. However, both types of machines may degrade because of excessive use and poor cleaning. Pumps are also more complicated mechanically, and can add to the cost of even simplest models. Certain espresso machines can eliminate the pump entirely and use steam pressure to brew espresso. The downside is that the boiler that produces steam also raises the temperature of water until it reaches boiling which can cause excessive extraction. The machines also need to continually rebuild their pressure between cups. This requires energy and time. Many espresso machines employ an rotary or vibrating pump, with a vibration model using a vibrating disc that generates the pressure and an rotary model that pushes hot water through the grounds under high speed. Both machines can make excellent espresso however rotary machines tend to be more stable, quieter and less likely to break down. The Boiler The boiler is what is used to heat the water to a temperature that is ideal for extraction. The resulting steam is then transferred to the portafilter, which contains the ground espresso coffee, and is then pumped into the cup. During coffee for espresso machine , the steam creates pressure to push through the grounds of the coffee. This creates a layer crema that is then poured over. This is a sign of a great espresso. There are three types of espresso makers. They differ in the type of pump they use and the degree of heat that the coffee is. There are a variety of ways to control the amount of brew, as well as the size of the cup that can be produced by the machine. The first espresso machines were steam type. They had only one boiler to make both brew and steam, but the pressure they could create was minimal – two bars of atmospheric pressure maximum. This resulted in the coffee tasting burnt and bitter. This is why the Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine. The most popular espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they think of these machines. 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 combination of human control and mechanised accuracy. The Filter Espresso machines typically use a filter that separates the grounds of coffee from hot water. The filter is also an essential component of the temperature control system, because it stops the machine from overheating. A filter also improves flavor because it allows for a longer flowering period. This allows the beans to release their nuances, and improves extraction. However it is crucial to keep in mind that even a top filter can result in a poor cup of coffee as the quality of the beans and extraction is still vital. It's in this area that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead (also called the brewhead) is where you put the portafilter, the thingy that you use to put the coffee grounds into, when making espresso. Steam-driven espresso machines use hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water into the coffee grounds under high pressure. These types of machines are generally cheaper and easier to maintain than pumps-driven models. They are however limited 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, compressed air-driven espresso machines have become more popular. They utilize an air compressor to force hot water through the ground and are more mobile than steam-driven electric espresso machines.