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How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and incredible filter technology to produce the perfect cup of coffee. But how exactly does it work?

Espresso is made by pushing hot water under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.

The Group Head

The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter before controlling the pressure of the extraction. There are many different types of group heads, each with its own advantages and disadvantages. Some are designed for temperature stability while others are built to handle pre-infusion. Others are built to control the lever. There are some that contain a variety of features, such as the E61, which is considered the standard choice for many baristas due to its capacity to provide multiple benefits in one package.

As you can see in the above image, the group head has several notches where you place your portafilter and then twist it manually to lock it in. There is also a gasket made of rubber which is located inside the notches, which helps create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact positioning of the portafilter which is necessary for a consistent extraction.

In addition to allowing you easily 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. It is important to remember that even a tiny variation can mean the difference between a good and excellent espresso.

The Pump

Contrary to manual piston machines which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure 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 types of machines are susceptible to degrading because of frequent use and insufficient cleaning. Pumps are also more complex mechanically, and can add to the price of even the most basic models.

Some espresso machines employ steam pressure instead of a pump for brewing espresso. This can lead to over-extraction as the boiler that makes steam also causes the water to boil. The machines must also continually rebuild their pressure between cups. This takes energy and time.

Many espresso machines utilize an rotary or vibrating pump, which is a vibration model using a rotating disc that generates the pressure, and rotating models that push hot water through the grounds under high speed. Both types of machines are capable of producing excellent espresso, but rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler will heat the water to the right temperature for extraction. The steam that is produced reaches the portafilter, which contains the ground espresso and is then pumped down into the cup. The steam creates enough pressure to push the grounds of the coffee through. This results in a crema on top of the espresso. This is a hallmark of a good espresso.

There are three types of espresso makers, and they differ in the type of pump they employ and how hot the coffee is. There are also different ways that the brew can be controlled and the size of the cup the maker can create.

The first uk espresso machine machines were steam type. They employed only one boiler to make steam and brew, however, the pressure they could create was minimal - two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most well-known espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp your 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

italian espresso machines machines typically use a filter that separates the grounds of the coffee from hot water. The filter is also an important component of the temperature control system as it keeps the machine from overheating.

A filter also improves flavor because it allows for a longer flowering phase. This helps the beans to release their flavors and provides an opportunity to improve extraction.

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

It's in this area that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead (also called the brewhead) is where you place the portafilter - the thingy used to place the grounds of coffee into when making espresso.

Steam-driven Cheap Espresso Machine machines use hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water through the grounds of coffee at high pressure. These kinds of machines are usually cheaper and easier to maintain than pump-driven models. They are however limited to create the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, espresso machines driven by compressed air-pump are becoming increasingly popular. They use an air compressor to force hot water through the grounds and are significantly more portable than electric steam-driven machines.