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How Does Machine Espresso Work? Machine espresso makes use of precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. How exactly does it work? To make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure. The Group Head The name implies, the group head is where you insert your portafilter when making espresso. It is responsible for dispersing water into the portafilter before controlling the pressure of the extraction. There are numerous kinds of group heads each with their own advantages and disadvantages. Some are designed for temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. Some come with a combination of both, like the E61. This is a very popular choice for baristas as it provides a variety of benefits in a single package. As you can see in the picture above the head of the group is fitted with a variety of notches. It is possible to place your portafilter into these notches and twist the head to lock it. A gasket made of rubber is positioned in the notches to create a seal while you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is necessary for an efficient extraction. In addition to allowing you to easily place your portafilter in, the group head is also responsible for maintaining an even temperature. It does this by cycling hot water through the brew basket and around the portafilter to ensure that it is always at the correct temperature to extract. This is crucial, since even a few degrees can be the difference between a good and excellent espresso. The Pump The motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure that is required for espresso extraction. This is different from manual piston machines that use levers. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pushed through the ground coffee inside the group head. Pumps tend to be cheaper than piston-driven machines, and they tend to last longer, although both types of machines may degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, which could increase prices of even simpler models. Some espresso machines make use of steam pressure instead of a pump to make espresso. This could lead to over-extraction since the boiler that produces steam also heats the water until it comes to a boil. Additionally these machines typically have to rebuild their pressure between cups, which takes time and energy. Many espresso machines make use of an rotary or a vibration pump. A vibration model uses a rotating disk to generate pressure, while the rotating model pushes hot water through the ground at a fast speed. Both machines can make excellent espresso however rotary machines tend to be more stable, quieter and less likely to break. The Boiler The boiler heats the water to the right temperature to extract. The resultant steam then reaches the portafilter which holds the ground espresso coffee and is then funneled down into the cup. The steam creates enough pressure to push the grounds of coffee through. This results in a layer crema on top. This is one of the main characteristics of a great espresso. There are discount espresso machines of espresso machines, each having a different type of pump and brew temperature. There are various ways that the brew can be controlled, as well as the dimensions of the cup the maker can create. The first espresso machines were steam-types. They utilized only one boiler to make both brew and steam, however, the pressure they could produce was very low – just two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. This is why the Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine. The most well-known espresso machine is a semiautomatic that has an electric pump. These are what people imagine when they think of an espresso machine. 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 an excellent compromise between human touch and the mechanized accuracy. The Filter Typically, espresso machines have filters to separate the coffee grounds as they pass through the hot water. The filter is also a vital element of the machine's temperature control, since it helps to prevent overheating. It also improves flavor, since a filter allows for a longer bloom phase. This lets the beans release their flavor and allows for a better extraction. It is important to remember that even the most efficient filter can produce a bad cup of coffee. The quality of the beans, and the extraction, are still crucial. This is where the magic happens, it's the thing that makes espresso taste great. The grouphead (also known as the brewhead) is where you place the portafilter – the thingy that you put the coffee grounds in, while making espresso. Steam-driven espresso machines use hot water heated in an airtight vessel to create steam. The steam then pushes hot water through coffee grounds under high pressure. These kinds of machines are generally cheaper and easier to maintain than pump-driven models. However, they are not as efficient in their ability to provide the ideal brewing conditions, because they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars. In recent times, espresso machines powered by compressed air-pump have become increasingly popular. They make use of an air compressor to push hot water across the ground, and are more mobile than electric steam-driven espresso machines.