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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. How exactly does it work?

Espresso is made by pushing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee, Machine Espresso but the key difference is in the pressure.

The Group Head

The name implies, the group head is the place you put your portafilter in when brewing espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are a variety of group heads, each with its own advantages and disadvantages. Some are designed to provide stability in temperature, while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some include a mix of features, like the E61 one, 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 image above, the group head has numerous notches that you can place your portafilter and then twist it with your hands to secure it. There is also a gasket of rubber in the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches allow for precise placement of your portafilter. This is vital for a consistent extraction.

The group head does not just allow you to put in your portafilter easily however, it also keeps an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it is always at the correct temperature for extraction. It is important to realize that even a slight difference can make the difference between a good and great espresso.

The Pump

In contrast to manual piston machines that use a lever to pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure that are required to extract espresso. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be less expensive and last for longer than piston-driven machines. However, both kinds of machines can degrade because of excessive use and poor cleaning. Pumps are also more complicated mechanically, which can increase prices of even simpler models.

Some espresso machines do away with the pump completely and make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that makes steam also heats the water until it comes to a boil. Additionally the machines often have to rebuild their pressure between cups, which requires time and energy.

Many espresso machines utilize either a rotary or vibration pump, which is a vibration model using a vibrating disc that generates the pressure and rotating models that push hot water through the grounds under high speed. Both machines can make great espresso, however rotary machines are more quiet, durable and less likely to break.

The Boiler

The boiler is what makes the water warm to the right temperature to extract. The steam created gets to the portafilter which is a container for espresso grounds. It is then poured into the cup. During this process the steam creates enough pressure to push the grounds of the coffee through. This results in a crema on the top of the espresso. This is one of the hallmarks of a good espresso.

There are three types of espresso makers, and they differ in the type of pump they employ and the degree of heat that the brew is. There are various ways to control the brew and the size of the cup that can be made by the machine.

The earliest espresso machines were steam-based. They used one boiler to make both steam and brew, however the pressure they were able to produce was very low - just two bars of atmospheric pressure at most. This resulted in the coffee tasting bitter and burnt. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most well-known espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they picture 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 great compromise between the human touch and the mechanised consistency.

The Filter

Typically, espresso machines employ filters to separate the coffee grounds as they pass through the hot water. The filter is also a vital component of the machine's temperature control, since it helps to prevent overheating.

Filters also aid in flavor as it allows for an extended flowering time. This allows the beans to release their nuances, and allows for better extraction.

However, it is important to keep in mind that even a great filter could result in a bad cup of coffee, because the quality of the beans and extraction are vital.

It's in this area that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead, also referred to as the brew head, is where the portafilter (the container you place the ground coffee in) is placed when making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to create steam. The steam then pushes hot water through grounds of the coffee under pressure. These kinds of machines are generally less expensive and easier to maintain than pump-driven models. However, they are not as efficient in their ability to create the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure, while the perfect 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 through the grounds, and are far more portable than electric steam-driven machines.