Maisie Birdwood

How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to create the delicious coffee we enjoy. How does it work exactly?

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

The Group Head

As the name suggests, the group head is where you place your portafilter while brewing espresso. It disperses water into the portafilter, and regulates the pressure of the extraction. There are a variety of types of group head, each with their distinct advantages and drawbacks. Some are focused on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. Some are a combination, such as the E61. This is a favorite among baristas due to the fact that it has multiple benefits in one package.

As you can see in the image above the group head is fitted with a variety of notches. It is possible to place your portafilter inside these notches, and then twist the head to secure it. A gasket of rubber is situated within the notches to create a seal as you insert your portafilter. The notches permit precise placement of your portafilter. This is vital for a consistent extraction.

The group head does not just allow you to place your portafilter easily, but it also maintains the same temperature. It does this by cycling hot water through the brew container and around the portafilter, ensuring that it's always at the correct temperature for extraction. It is important to realize that even a tiny difference can make the difference between a good and great espresso coffee makers.

The Pump

Contrary to manual piston machines which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure required for espresso extraction. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.

Pumps tend to be less expensive than piston-driven machines, and tend to last longer, but both types of machines can get damaged through overuse and lack of cleaning. They also make mechanically complex which can result in a high price tag on even the most basic models.

Certain espresso machines eliminate the pump completely and instead make use of steam pressure to make espresso. This could lead to over-extraction since the boiler that makes steam also warms the water to boil. These machines also have to constantly rebuild their pressure between cups. This requires energy and time.

Many espresso machines employ an rotary or vibrating pump, which is a vibration model using a rotating disc to create the pressure and the rotary model pushing hot water through the grounds at high speed. Both machines can make excellent espresso however rotary machines tend to be more quiet, durable and less likely to break down.

The Boiler

The boiler is what is used to heat the water to a temperature that is ideal to extract. The resulting steam is then transferred to the portafilter, which contains ground espresso beans and is then pumped into the cup. The steam is able to create enough pressure to push the grounds of the coffee through. This creates a foam on the top of the italian espresso machines. This is a hallmark of a great espresso.

There are three distinct types of espresso machines, each having different types of pumps and brew temperature. There are also different ways in which the brew could be controlled, as well as the dimensions of the cup the machine can make.

The first espresso machines were steam-type. They utilized only 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 maximum. This led to the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic espresso machine, you grind the beans and tamp them yourself but the pump controls the flow of water and pressure. This is an excellent compromise between human control and mechanised accuracy.

The Filter

Typically, espresso machines utilize a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also a crucial part of the temperature control system, as it keeps the machine from overheating.

A filter also improves flavor since it allows for a longer flowering period. This lets the beans release their flavors, and allows for a better extraction.

However it is crucial to remember that even a high-quality filter can result in a poor cup of coffee, because the quality of the beans and extraction is crucial.

This is where the magic happens. It's what makes an compact espresso machine really taste great. The grouphead, often referred to as the brew head, is the place where the portafilter (the container you place the coffee grounds into) is placed when making Italian espresso machines.

Steam-driven espresso machines use hot water heated in an airtight container to produce steam. The steam then moves hot water through the grounds of coffee at high pressure. These kinds of machines are usually cheaper and easier to maintain than pumps-driven models. They are however limited to create the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent times, mini espresso machine machines powered by a compressed air pump have become increasingly popular. They use an air compressor to force hot water into the ground and are more mobile than electric steam-driven espresso machines.