How Does Machine Espresso Work?

Machine espresso employs precise pressure and incredible filter technology to produce the coffee we love. What exactly does it work?

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

The Head of the Group

The group head is the portafilter you place in the espresso maker when making it. It disperses water in the portafilter, and regulates the pressure of the extraction. There are various kinds of group heads, each with their unique advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion features, and others are designed to control the lever. Some include a combination like the E61. This is a favorite among baristas because it offers multiple benefits in a single package.

As you can see from the photo above the group head is equipped with several notches. It is possible to place your portafilter in these notches and then twist the head to lock it. There is also a gasket made from rubber that resides inside the notches to help create the seal when you insert your portafilter into the machine. The notches allow for the precise placement of the portafilter. This is essential for an even extraction.

The group head does not just allow you to place your portafilter easily however it also keeps an even temperature. This is done by cycling hot water around the portafilter, and through the brew-basket to ensure the temperature is always right for extraction. It is important to realize that even a few degree differences can make the distinction between a great and a excellent espresso machine with frother.

The Pump

Unlike manual piston machines, that use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure that are required for espresso extraction. The pressure is created by drawing tap water from a reservoir and pumping it through a heat exchanger before it is shot through the ground coffee in the group head.

Pumps tend to be cheaper than piston-driven machines, and tend to last longer, however both types of machine can become damaged due to excessive use and poor cleaning. They also make mechanically complex and can lead to an expensive price for even the most basic models.

Some espresso machines eliminate the pump completely and instead use steam pressure to brew espresso. This can lead to over-extraction as the boiler that produces steam also heats the water until it comes to a boil. Additionally, these machines frequently have to restore their pressure between cups, which takes time and energy.

Many espresso machines employ an rotary or vibrating pump, with a vibration model using a rotating disc to generate the pressure, and the rotary model pushing hot water through the grounds under high speed. Both machines can produce excellent espresso, however rotary machines are quieter, more durable and less likely to fail.

The Boiler

The boiler is what is used to heat the water to the ideal temperature to extract. The resultant steam then reaches the portafilter that contains the ground espresso coffee, and gets funnelled down into the cup. The steam creates enough pressure to push the grounds of coffee through. This creates a foam on the top espresso machines of the espresso. This is one of the main characteristics of a good espresso.

There are three kinds of espresso makers. They differ in the kind of pump they use and how hot the espresso is. There are a variety of ways to control the amount of brew, as well as the size of cup that can be made by the machine.

The first espresso machines were steam-type. They employed one boiler to make both brew and steam, but the pressure they could generate was low - only two bars of atmospheric pressure maximum. This led to the coffee tasting bitter and burnt. The modern home espresso machine machine was developed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso machine is a semiautomatic model with an electric pump. When people think of espresso machines, they picture these machines. If you have a semi-automatic machine you must grind the beans and then tamp them by hand, but the pump controls the flow of water and pressure. This is an excellent compromise between human touch and mechanized consistency.

The Filter

Typically, espresso machines utilize filters that separate the grounds of coffee when they pass through the hot water. The filter is also a vital component of the machine's temp control, since it stops overheating.

A filter also improves flavor, as it permits an extended flowering time. This helps the beans to release their flavors and provides an opportunity for a better extraction.

It is important to keep in mind that even the most efficient filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, remain vital.

This is where the magic happens, and it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you put the portafilter, the device which you put the coffee grounds in, when making espresso.

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

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