How Does Machine Espresso Work?

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

Espresso is made by pushing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee. However the pressure is the primary difference.

The Group Head

As the name implies, the group head is the place you put your portafilter in when brewing espresso. It distributes water into the portafilter and regulates the pressure during the extraction. There are a variety of group heads each with their own advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. There are even some that contain a variety of features, like the E61 one, which is the standard choice for many baristas because of its ability to offer multiple benefits in a single package.

As you can see in the above image the group head comes with numerous notches that you can place your portafilter and twist it by hand to lock it in. A rubber gasket is located within the notches to create a seal as you insert your portafilter. The notches allow for precise placement of the portafilter. This is essential for an even extraction.

The group head not only lets you to insert your portafilter easily but also maintains a constant 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. This is vital, because even a small difference in temperature can make the difference between a good and great buy espresso makers.

The Pump

The motorized pumps used in espresso machines rotary provide nine atmospheric bar pressure needed to extract espresso. This differs from manual piston machines that rely on a lever. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.

Pumps tend to be cheaper than piston-driven machines, and tend to last longer. However, both types of machines may get damaged through overuse and lack of cleaning. They also make mechanically complex and can lead to costly prices for even the simplest models.

Some espresso machines employ steam pressure instead of a pump in order to brew espresso. The drawback is that the same boiler that produces steam also raises the temperature of water to the point of boiling and can result in excessive extraction. Additionally these machines are often required to rebuild their pressure between cups, which requires time and energy.

A majority of espresso machines use the rotary or vibration pump, with a vibration model that uses a vibrating disc to create the pressure, and the rotary model pushing hot water through the grounds under high speed. Both models can make a great espresso, but Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the element that heats the water to the optimal temperature for extraction. The steam that is created will eventually reach the portafilter, which holds the best home espresso machine grounds. It is then pumped into the cup. In this process, the steam creates pressure and pushes through the grounds of the coffee. This creates a foam on the top of the espresso. This is one of the hallmarks of a good espresso.

There are three kinds of espresso machines, each having a different type of pump and the temperature of the brew. There are a variety of ways to control the amount of brew, as well as the size of the cup that can be made by the machine.

The first espresso machines were steam-types. They used a single boiler to make both brew and steam, but the pressure they could generate was low - only two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. The modern professional espresso machine for home machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso maker is a semi-automatic machine with an electric pump. This is what people envision when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans on your own, but the pump regulates the flow of water and pressure. This is an excellent combination of human control and mechanised reliability.

The Filter

Espresso machines usually use filters that separate the grounds of the coffee from the hot water. The filter is also an essential component of the machine's temp control, since it helps to prevent overheating.

A filter also improves flavor because it allows for a longer flowering phase. This lets the beans let their nuances out, and allows for better extraction.

However, it is important to remember that even a high-quality filter can make a terrible cup of coffee, because the quality of the beans and extraction is still vital.

It's in this area that the magic happens. This is the reason why espresso tastes so good. The grouphead (also known as the brewhead) is where you place the portafilter, the device that you use to put the coffee grounds into, while making espresso.

Steam-driven espresso machines make use of hot water that is heated in an airtight container to produce steam. The steam then moves hot water through the grounds of the coffee under pressure. These kinds of machines tend to be less expensive and easier to maintain than pump-driven models. They are however limited in their ability for creating the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, compressed air pump-driven espresso machines have been gaining popularity. They utilize an air compressor to push hot water through the grounds and are much more portable than steam-driven electric machines.