How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. 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, 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 while making espresso. It disperses water into the portafilter and regulates the pressure of the extraction. There are many different kinds of group head each with its distinct advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion options, and others are designed to control the lever. There are some that contain a variety of features, like the E61, which is the most popular choice among baristas due to its ability to provide multiple benefits in a single package.

As you can see in the picture above, the group head is fitted with a variety of notches. You place your portafilter in these notches, then turn the head around to secure it. There is also a gasket made of rubber in the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is crucial for an accurate extraction.

Apart from allowing you easily connect your portafilter, the group head is responsible for maintaining a consistent temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is always at the right level for extraction. This is important because just a few degrees could be the difference between a good and excellent espresso.

The Pump

Contrary to manual piston machines that use a lever to pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure necessary to extract cheap espresso machine. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being shot through the ground coffee in the group head.

Pumps tend to be cheaper than piston-driven models, and they tend to last longer, however both types of machines may get damaged through overuse and lack of cleaning. They also create mechanical complexity and can lead to a high price tag on even the most basic models.

Some espresso machines can eliminate the pump completely and make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that produces steam also heats the water until it comes to a boil. The machines must also constantly rebuild their pressure between cups. This requires energy and time.

Many espresso machines employ a vibration or rotary 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 types of machines are capable of producing excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the one that will heat the water to a temperature that is ideal for extraction. The steam created is then directed to the portafilter, which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. In this process, the steam causes pressure to push through the coffee grounds. This creates a crema on top of the espresso. This is one of the hallmarks of a great espresso.

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

The first best cheap espresso machine machines were steam-type. They had a single boiler to make both brew and steam, but the pressure they could create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp your beans yourself however the pump controls the water flow and pressure. This is a great solution that combines human control with mechanized consistency.

The Filter

Espresso machines usually use filters that separate the coffee grounds from the hot water. The filter is also an essential component of the temperature control system, as it prevents the machine from overheating.

A filter also improves flavor because it allows for an extended flowering time. This allows the beans to let their nuances out and provides an opportunity for better extraction.

It is important to remember that even the most efficient filter can result in a bad cup of coffee. The quality of the beans and the extraction process remain crucial.

This is where the magic happens, and it's what makes espresso taste good. The grouphead, also referred to as the brewhead, is where the portafilter (the device you put the coffee ground into) is placed when you're making espresso.

In a steam-driven retro espresso machine machine hot water is heated in an airtight tank to produce steam, which then pushes the hot water through the grounds at high pressure. These kinds of machines are typically cheaper and easier to maintain than pumps-driven models. They are however limited to create the perfect conditions for brewing, as they 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 become more popular. They make use of an air compressor to push hot water across the ground. They are also more mobile than electric steam-driven espresso machines.