How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and incredible filter technology to produce the delicious coffee we enjoy. But how exactly does it work?

Espresso is created by forcing hot water under high 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 the place you place your portafilter when making espresso. It is responsible for dispersing water into the portafilter before controlling the pressure that results from the extraction. There are a variety of group heads each with their own advantages and disadvantages. Some focus on temperature stability, whereas others on pre-infusion options, and others are designed to control the lever. There are some that include a mix of features, like the E61, which is considered the standard choice for many baristas because of its ability to offer multiple benefits in a single package.

As you can see in the photo above, the group head is fitted with several notches. You place your portafilter in these notches and then twist the head to secure it. There is also a gasket made of rubber that is a part of the notches and helps to create a seal when you insert your portafilter into the machine. The notches permit an exact placement of the portafilter. This is crucial for a consistent extraction.

Apart from allowing you easily connect your portafilter, the group head is also responsible for maintaining 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 to extract. This is vital, because just a few degrees could be the difference between a good and excellent pro espresso machine.

The Pump

The motorized pumps in espresso maker barista machines rotary provide nine atmospheric bar pressure required for espresso extraction. This is different from manual piston machines that rely on levers. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be cheaper than piston-driven machines, and they tend to last longer. However, both types of machine can be damaged by excessive use and inadequate cleaning. They also add mechanical complexity, which can result in a high price tag on even the simplest models.

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

Many espresso machines employ either a rotary or vibration pump, which has a vibration model using a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds at high speed. Both machinestion, are still very important.

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

Steam-driven retro espresso maker (website) machines use hot water that is heated inside an airtight vessel to create steam. The steam then moves hot water through the coffee grounds under high pressure. These kinds of machines tend to be cheaper and easier to maintain than pump-driven models. However, they are not as efficient in their capacity to create the perfect brewing conditions as they only operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.

In recent years, espresso machines driven by a compressed air pump have become increasingly popular. They utilize an air compressor to force hot water into the ground. They are also more mobile than electric steam-driven espresso machines.