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How Does Machine Espresso Work?

Machine espresso uses precision pressure and amazing filter technology to make the coffee we love. How exactly does it work?

To make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.

The Head of the Group

As the name implies the group head is the place you put your portafilter in when making espresso. It disperses water into the portafilter, and regulates the pressure during the extraction. There are numerous kinds of group heads each with its own advantages and drawbacks. Some are specifically designed for coffee and espresso maker stability of temperature while others are built to handle pre-infusion. Others are made to control the lever. Some are a combination, like the E61. This is a favorite among baristas because it offers multiple advantages in one package.

As you can see from the above photo the head of the group is fitted with a variety of notches. It is possible to place your portafilter into these notches and turn the head around to secure it. A rubber gasket is located inside the notches to help create a seal when you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is vital for an even extraction.

In addition to allowing you easily place your portafilter in, 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, making sure that the temperature is always at the right level for extraction. It is important to realize that even a small espresso machine deviation can make the difference between a great and a excellent espresso.

The Pump

In contrast to manual piston machines which use a lever to pressurize water, rotating commercial espresso machine machines espresso rely upon motorized pumps to supply the nine atmospheric bars of pressure needed to extract espresso. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee espresso machines.

Pumps are generally cheaper and last longer than piston-driven machines. However, both types of machines may degrade because of frequent use and insufficient cleaning. They also increase the complexity of mechanical systems and can lead to a high price tag on even the simplest models.

Some espresso machines do away with the pump completely and utilize steam pressure to make espresso. The downside is that the same boiler that produces steam also increases the temperature of water until it reaches boiling and can result in over-extraction. The machines also need to constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines use an rotary or a vibration pump. A vibration model uses an oscillating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at a high speed. Both machines can produce excellent espresso but rotary machines are more quiet, durable and less likely to break down.

The Boiler

The boiler is what makes the water warm 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 pumped into the cup. The steam is able to create enough pressure to push the coffee grounds through. This results in a layer crema on top. This is one of the main characteristics of a great espresso.

There are three distinct types of retro espresso machine machines, each with different types of pumps and the temperature of the brew. There are a variety of ways to control the amount of brew, as well as the size of cup that can be produced by the machine.

The first espresso machines were steam-types. The earliest espresso machines were steam types. This resulted in the coffee tasting burnt and bitter. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most popular espresso maker is a semi-automatic device with an electric pump. When people think of espresso machines, they imagine these machines. With a semi-automatic machine you have to grind the beans and tamp them by hand, but the pump provides regulated water flow and pressure. This is a perfect solution that combines human control with mechanised accuracy.

The Filter

Espresso machines usually use filters that separate the grounds of coffee from hot water. The filter is also a vital part of the machine's temperature control, since it stops overheating.

A filter also helps with flavor as it allows for an extended flowering time. This allows the beans to release their nuances, and allows for a better extraction.

However, it is important to remember that even a high-quality filter can produce a bad cup of coffee, as the quality of the beans and extraction is still vital.

It's here that the magic takes place. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you put the portafilter, which is the thingy used to place the grounds of your coffee and espresso maker - Read This method, into when making espresso.

In a steam-driven espresso machine hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds at a high pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. They are however limited in their ability for creating 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, compressed air-pump-driven espresso machines have become more popular. They make use of an air compressor to push hot water through the ground, and are more mobile than steam-driven electric espresso machines.