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How Does Machine Espresso Work?

Machine espresso coffee maker makes use of precise pressure and amazing filter technology to make the delicious coffee we enjoy. What exactly is it that makes it work?

In order 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

As the name implies, the group head is where you put your portafilter in when brewing espresso. It disperses water in the portafilter, and then regulates the pressure of extraction. There are numerous kinds of group heads each with distinct advantages and disadvantages. Some are designed for temperature stability while others are designed to handle pre-infusion. Others are built to control the lever. Some come with a combination of both, such as the E61. This is a preferred choice for baristas as it provides a variety of advantages in one package.

As you can see in the photo above, the group head has several notches where you place your portafilter and then twist it with your hands to lock it in. A rubber gasket is located inside the notches, which helps create a seal as you insert your portafilter. The notches allow for precise placement of the portafilter. This is crucial to ensure a consistent extraction.

In addition to allowing you easily connect your portafilter, the group head is responsible for maintaining an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket, making sure the temperature is always right to extract the coffee. This is important because even a small difference in temperature can mean the difference between good and great espresso.

The Pump

The motorized pumps used in rotary espresso machines supply the nine atmospheric bar pressure that is required for espresso extraction. This differs from manual piston machines that rely on a lever. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger prior being pumped through the ground coffee inside the group head.

Pumps are typically less expensive than piston-driven models, and they tend to last longer, however both types of machine can get damaged through overuse and lack of cleaning. They also add mechanical complexity and can lead to a high price tag on even the most basic models.

Certain espresso machines remove the pump completely and instead employ steam pressure to create espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of water to the point of boiling which could lead to excessive extraction. These machines also have to constantly rebuild their pressure between cups. This requires energy and time.

A majority of espresso machines use either a rotary or vibration pump, which has a vibration model using a rotating disc to create pressure and rotating models that push hot water through the grounds under high speed. Both machines can make excellent espresso but rotary machines are more stable, quieter and less likely to fail.

The Boiler

The boiler will heat the water to the right temperature to extract. The steam that is produced reaches the portafilter which holds the ground espresso coffee, and is then pumped into the cup. During this process, steam causes pressure to push through the grounds of the coffee. This results in a layer crema that is then poured over. This is one of the main characteristics of a great espresso.

There are three kinds of espresso makers, which differ in the type of pump they use and the degree of heat that the brew is. There are also different ways in which the brew could be controlled as well as the dimensions of the cup the maker can create.

The first espresso machines were steam-type. They employed only one boiler to make both steam and brew, however the pressure they were able to produce was not very high - two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most well-known espresso maker is a semi-automatic one with an electric pump. These are what people imagine when they think of an espresso machine small machine. Semi-automatic machines require you to grind and tamp the beans by yourself, but the pump regulates the water flow and pressure. This is an excellent compromise between human touch and the mechanised accuracy.

The Filter

Espresso machines typically have a filter that separates the grounds of coffee from hot water. The filter is also a vital component of the machine's temperature control, as it prevents overheating.

It also improves flavor, as a filter lets you enjoy a longer bloom phase. This helps the beans let their nuances out and provides an opportunity for better extraction.

However, it is important to keep in mind that even a good filter can make a terrible cup of coffee as the quality of the beans and extraction are essential.

This is where the magic happens, and it's what makes espresso taste good. The grouphead (also called the brewhead) is where you put the portafilter, the thingy that you use to put the coffee espresso machine grounds into, when making espresso.

In a steam-driven espresso machine hot water is heated in an airtight container bean to cup espresso machines produce steam, which then pushes the hot water through the grounds under high pressure. These machines are less expensive and easier to maintain than pumps-driven models. They are however limited to create the perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, compressed air-driven espresso machines have been gaining popularity. They use an air compressor to push the hot water through the grounds and are significantly more portable than electric steam-driven machines.