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How Does Machine Espresso Work? Machine espresso makes use of precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. How exactly does it work? 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 key difference is in the pressure. The Head of the Group The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure of the resulting extraction. There are many different kinds of group heads, each with their unique advantages and disadvantages. Some are designed for temperature stability while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some have a combination, like the E61. This is a popular choice among baristas as it provides a variety of advantages in a single package. As you can see in the photo above the group head is fitted with several notches. You can place your portafilter in these notches, then twist the head to secure it. There is also a rubber gasket in the notches and helps to create a seal when you insert your portafilter into the machine. The notches on the head permit an exact position of the portafilter which is essential to ensure an efficient extraction. In addition to allowing you effortlessly insert your portafilter the group head is responsible to maintain an even temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket, ensuring that the temperature is at the right level to extract the coffee. This is vital, because even a small difference in temperature can make the difference between good and excellent espresso. The Pump Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure required for espresso extraction. This differs from manual piston machines that rely on a lever. The pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being pushed through the ground coffee in the group head. Pumps are typically less expensive than piston-driven models, and they tend to last longer, but both types of machines can get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, which can raise the price of even the simple models. Some espresso machines can eliminate the pump completely and instead employ steam pressure to create espresso. The disadvantage of this is that the same boiler that produces steam also raises the temperature of the water to the point of boiling which could lead to over-extraction. Additionally these machines are often required to rebuild their pressure between cups, which requires time and energy. Many espresso machines use an rotary or a vibration pump. A vibration model utilizes an oscillating disk to create pressure, while a rotary model pushes hot water through the ground at high speed. coffeee.uk of machines can produce an excellent espresso, however Rotary machines are quieter and more durable than vibration pumps. The Boiler The boiler is the component which heats the water to the ideal temperature to extract. The resultant steam then reaches the portafilter containing ground espresso beans and is then funneled down into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This results in a crema on top of the espresso. This is one of the main characteristics of a great espresso. There are three types of espresso machines, each having distinct pumps and brew temperature. There are different ways that the brew can be controlled and the size of the cup the maker can create. The first espresso machines were steam type. They had one boiler to make both brew and steam, however, the pressure they could produce was very low – just two bars of atmospheric pressure maximum. This resulted in the coffee tasting burnt and bitter. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine. The most common espresso maker is a semiautomatic machine with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the flow of water and pressure. This is a perfect compromise between human control and mechanised consistency. The Filter Espresso machines typically have filters that separate the coffee grounds from the hot water. The filter is also a vital component of the machine's temperature control, since it stops overheating. A filter also improves flavor as it allows for a longer flowering phase. This allows the beans to release their nuances, and allows for better extraction. However it is crucial to remember that even a high-quality filter can make a terrible cup of coffee, since the quality of the beans and extraction is still crucial. This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead (also known as the brewhead) is where you place the portafilter, the device that you put the coffee grounds in, when making espresso. Steam-driven espresso machines use hot water that is heated in an airtight container to create steam. The steam then pushes hot water through the grounds of coffee under high pressure. These types of machines are typically less expensive and simpler to maintain than pumps-driven models. However, they are limited in their ability to provide the ideal conditions for brewing as they only operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar. In recent times, espresso machines powered by compressed air-pump have become increasingly popular. They utilize an air compressor to push hot water through the grounds and are significantly more portable than steam-driven electric machines.