How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to create the coffee and espresso maker we love. How exactly does it work?

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

The Group Head

As the name suggests, the group head is where you put your portafilter in when making espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the extraction. There are a variety of types of group heads each with its distinct advantages and disadvantages. Some are specifically designed for stability of temperature while others are built to handle pre-infusion. Some are designed to control the lever. There are some that contain a variety of features, such as the E61, which is to be the most popular among baristas for its ability to offer multiple benefits in a single package.

As you can see from the above photo, the group head is fitted with several notches. The portafilter is placed inside these notches, and then turn the head around to secure it. There is also a gasket of rubber in the notches and Machine espresso helps to create a seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is crucial for a consistent extraction.

Apart from allowing you easily place your portafilter in, the group head is also responsible to ensure that the temperature remains even. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it's always at the correct temperature for extraction. It is important to remember that even a few degree variation can mean the difference between a decent and a great espresso.

The Pump

Motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure needed for espresso extraction. This is different from manually operated piston machines that employ a lever. The pressure builds by removing 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 are typically cheaper and last longer than piston-driven machines. However, both kinds of machines may degrade because of frequent use and inadequate cleaning. They also add mechanical complexity which can result in an expensive price for even the simplest models.

Some espresso machines employ steam pressure instead of a pump to make espresso. This could lead to over-extraction since the boiler that produces steam also causes the water to boil. The machines must also constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines use an rotary or a vibration pump. A vibration model uses a vibrating disk to generate pressure, whereas the rotary model pushes hot water through the ground at high speed. Both types of machines can make a great espresso, however the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the element that heats water to an ideal temperature for extraction. The steam created gets to the portafilter which is the container that holds the espresso coffee grounds. It is then poured into the cup. During this process the steam generates enough pressure to push the coffee grounds through. This creates a layer crema on top. This is one of the main characteristics of a great espresso.

There are three different types of espresso machines, each with different pumps and the temperature of the brew. There are a variety of ways in which the brew could be controlled, as well as the size of the cup the maker can create.

The first espresso machine with grinder machines were steam-type. They had one boiler to make both brew and steam, however the pressure they were able to generate was low - only two bars of atmospheric pressure, at most. This resulted in the coffee tasting burnt and bitter. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most commonly used espresso maker is a semi-automatic device that has an electric pump. This is what people envision when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the flow of water and pressure. This is a great combination of human control and mechanised reliability.

The Filter

Typically, espresso machines use filters to separate the grounds of coffee as they move through the hot water. The filter is also a vital part of the temperature control system since it helps prevent the machine from overheating.

It also enhances flavor, as a filter can allow for a longer bloom phase. This lets the beans release their nuances, and improves extraction.

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

It's here that the magic takes place. This is the reason why espresso tastes so good. The grouphead, often referred to as the brewhead, is where the portafilter (the thingy you put the coffee grounds into) is placed when you're making espresso.

Steam-driven espresso machines make use of hot water heated in an airtight vessel to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. They are however limited in their ability 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 times, espresso machines powered by compressed air-pump are becoming increasingly popular. They use an air-compressor to push hot water across the ground, and are more mobile than steam-driven electric espresso machines.