How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. But how exactly does it work?

To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee machine espresso. However it is the pressure that makes the main difference.

The Head of the Group

As the name implies the group head is where you place your portafilter when making espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure that results from the extraction. There are a variety of group heads each with distinct advantages and disadvantages. Some are designed for temperature stability while others are specifically designed to handle pre-infusion. Others are made to control the lever. Some have a combination, like the E61. This is a preferred choice for baristas due to the fact that it has multiple benefits in a single package.

As you can see in the image above The group head features several notches to place your portafilter and twist it by hand to secure it. There is also a gasket made of rubber which is located inside the notches and helps create a seal when you insert your portafilter into the machine. The notches on the head permit a precise placement of the portafilter, which is vital for an even extraction.

The group head does not just allow the portafilter to be inserted easily, but it also maintains the same temperature. This is accomplished by cycling hot water around the portafilter and through the brew-basket bean to cup espresso machines ensure the temperature is always right to extract the coffee. This is important because even a few degrees can make the difference between good and excellent espresso.

The Pump

Motorized pumps in rotary espresso machines supply the nine atmospheric bar pressure that is required for espresso extraction. This is different from manual piston machines which use levers. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger before being shot through the ground coffee inside the group head.

Pumps are typically less expensive and last longer than piston-driven machines. However, both types of machines may degrade due to overuse and inadequate cleaning. Pumps are also more complex mechanically, which could increase prices of even most basic models.

Some espresso machines make use of steam pressure instead of a pump for brewing espresso. This could lead to over-extraction since the boiler that produces steam also causes the water to boil. These machines also have to continually rebuild their pressure between cups. This requires energy and time.

A majority of espresso machines use either a rotary or vibration pump, which is a vibration model using a rotating disc that generates the pressure, and In recent years, compressed-air-pump-driven espresso machines have become more popular. They utilize an air compressor to push hot water through the ground and are much more mobile than electric steam-driven espresso machines.