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How Does Machine Espresso Work? Machine espresso utilizes precise pressure and amazing filter technology to make the perfect cup of coffee. What exactly is it? To make an espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference. The Group Head The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the extraction. There are many different kinds of group head, each with their own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. There are some that come with a range of features, such as the E61, which is the classic choice among many baristas because of its ability to offer multiple benefits in a single package. As you can see in the photo above the group head is made up of several notches where you place your portafilter before twisting it manually to secure it. A gasket made of rubber is placed in the notches to create a seal as you insert your portafilter. The notches on the head permit an exact location of the portafilter which is crucial for a consistent extraction. The group head does not just allow you to put in your portafilter easily however it also keeps the temperature at a constant level. This is done by cycling hot water around the portafilter, and through the brew-basket, making sure the temperature is always right for extraction. This is important because even a small difference in temperature can make the difference between good and excellent espresso. The Pump The motorized pumps that are used in espresso machines rotary provide nine atmospheric bar pressure needed for espresso extraction. This is different from manually operated piston machines that employ a lever. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee. Pumps are generally less expensive and last for longer than piston-driven machines. However, both types of machines are susceptible to degrading because of frequent use and inadequate cleaning. They also increase the complexity of mechanical systems which can result in costly prices for even the simplest models. Certain espresso machines eliminate the pump entirely and utilize steam pressure to make espresso. This could lead to over-extraction since the boiler that makes steam also warms the water to boil. The machines also need to continuously rebuild their pressure between cups. This takes energy and time. A majority of espresso machines utilize the rotary or vibration pump. A vibration model employs the vibrating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at a fast speed. Both machines produce great espresso but rotary machines are more quiet, durable and less likely to break down. The Boiler The boiler is what is used to heat the water to the ideal temperature for extraction. The steam produced reaches the portafilter, which is the container that holds the espresso coffee grounds. It is then poured into the cup. During this process the steam causes enough pressure to push the grounds of coffee through. This creates a crema on top of the espresso. This is a hallmark of a great espresso. There are three kinds of espresso machines, each having a different type of pump and brew temperature. There are a variety of ways to control the strength of the brew and the size of cup that can be made by the machine. coffeee.uk were steam-based. They used one boiler to make both steam and brew, but the pressure they could generate was low – only two bars of atmospheric pressure, at most. This led to the coffee tasting bitter and burnt. The modern espresso machine was created by the Milanese makers Luigi Bezzerra & Desiderio Pavoni. The most popular espresso maker is a semi-automatic one with an electric pump. These are the images people have when they think of an espresso machine. Semi-automatic machines require you to grind and tamp your beans yourself while the pump controls the water flow and pressure. This is an excellent compromise between human touch and the mechanized consistency. The Filter Typically, espresso machines have filters that separate the grounds of coffee when they pass through the hot water. The filter is also a crucial element of the temperature control system, since it helps prevent the machine from overheating. A filter also helps with flavor since it allows for a longer flowering period. This helps the beans to release their nuances and gives an opportunity for better extraction. However it is crucial to keep in mind that even a top filter could result in a bad cup of coffee, since the quality of the beans and extraction are important. This is where the magic happens, and it's what makes an espresso really taste good. The grouphead (also known as the brewhead) is where you place the portafilter, which is the thingy that you use to put the coffee grounds in, 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 through grounds of the coffee under pressure. These machines are cheaper and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars. In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air compressor to push hot water into the grounds and are significantly more portable than electric steam-driven machines.