How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to create the perfect cup of coffee. How does it work exactly?

In order to make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure.

The Head of the Group

The name implies the group head is the place you place your portafilter when making espresso. It disperses the water into the portafilter, and regulates the pressure during the extraction. There are various kinds of group head each with its own advantages and drawbacks. Some are focused on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. Some include a mix of features, such as the E61, which is to be the most popular among baristas for its ability to offer multiple benefits in one package.

As you can see in the photo above the group head comes with several notches to put your portafilter, then twist it with your hands to lock it in. A gasket made of rubber is placed in the notches to create a seal when you insert your portafilter. The notches on the head permit a precise position of the portafilter which is necessary to ensure an even extraction.

The group head not only lets the portafilter to be inserted easily however it also keeps an even temperature. It does this by cycling hot water through the brew basket and around the portafilter to ensure that it's always at the correct temperature to extract. This is vital, Machine Espresso because just a few degrees could mean the difference between excellent and great espresso.

The Pump

In contrast to manual piston machines which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by pumping water through a heat exchanger and then through the ground coffee.

Pumps are generally 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 complicated mechanically, which can increase prices of even simplest models.

Some espresso machines do away with the pump entirely and utilize steam pressure to make espresso. The drawback is that the same boiler that produces steam also raises the temperature of water until it reaches boiling which can cause over-extraction. Additionally the machines often have to rebuild their pressure between cups, which takes time and energy.

A large majority of espresso machines employ either a vibration or rotary pump. A vibration model makes use of a rotating disk to generate pressure, while the rotating model pushes hot water through the ground at a high speed. Both machines produce great best budget espresso machine but rotary machines are quieter, more durable and less likely to break down.

The Boiler

The boiler is used to heat the water to a temperature that is ideal for extraction. The steam that is produced reaches the portafilter, which contains the ground espresso coffee and is then pumped into the cup. In this process, the steam creates pressure and pushes through the grounds of the coffee. This results in a whipped-up the top of the espresso. This is one of the hallmarks of a great espresso.

There are three types of espresso machines, each having a different type of pump and brew temperature. There are a variety of ways in which the brew can be controlled as well as the dimensions of the cup the machine can produce.

The first espresso machines were steam types. They used one boiler to create both steam and brew however, the pressure they could produce was very low - just two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most popular espresso maker is a semi-automatic machine that has an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic machine you must grind the beans and tamp them yourself but the pump regulates the flow of water and pressure. This is a great combination of human control and mechanized consistency.

The Filter

Typically, espresso machines have filters that separate the grounds of coffee when they pass through the hot water. The filter is also an important component of the temperature control system, as it prevents the machine from overheating.

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

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

It's in this area that the magic occurs. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you place the portafilter, the thingy which you put the coffee grounds in, when making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight tank to produce steam, which then pushes the hot water through the grounds at a high pressure. They are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited to create the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

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