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How Does Machine Espresso Work?

Machine espresso uses precision pressure and incredible filter technology to produce the coffee we love. What exactly is it that makes it work?

To make an espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However the pressure is the main difference.

The Group Head

The group head is the portafilter that you place in the espresso maker when making it. It disperses water in the portafilter, and then regulates the pressure of extraction. There are a variety of group heads each with distinct advantages and disadvantages. Some are designed for stability of temperature while others are designed to handle pre-infusion. Others are made to control the lever. Some contain a variety of features, such as the E61, which is to be the most popular among baristas due to its capacity to offer multiple perks in a single package.

As you can see in the photo above The group head features several notches where you place your portafilter and twist it with your hands to secure it. A gasket made of rubber is positioned inside the notches to help make a seal when you insert your portafilter. The notches permit an exact placement of the portafilter. This is vital for an even extraction.

Aside from allowing you to easily connect your portafilter, the group head is responsible to maintain an even temperature. It does this by cycling hot water through the brew pan and around the portafilter, making sure that it's always at the correct temperature for extraction. It is important to realize that even a tiny differences can make the distinction between a good and excellent espresso.

The Pump

Unlike manual piston machines, which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure needed for espresso extraction. The pressure is created by removing tap water from a reservoir and pumping it through a heat exchanger prior to it is shot through the ground coffee inside the group head.

Pumps tend to be cheaper than piston-driven models, and they tend to last longer, however both types of machines may degrade with overuse and insufficient cleaning. They also create mechanical complexity which can result in the cost of even the simplest models.

Some italian espresso machines machines use steam pressure instead of a pump in order to brew espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of water until it reaches boiling, which can lead to excessive extraction. The machines must also constantly rebuild their pressure between cups. This requires energy and time.

Many espresso machines make use of the rotary or vibration pump. A vibration model uses a rotating disk to generate pressure, whereas the Rotary model pushes hot coffee through the ground at a high speed. Both machines can make excellent espresso, but rotary machines are quieter, more durable and less likely to break.

The Boiler

The boiler is what makes the water warm to the right temperature to extract. The steam that is created gets to the portafilter which contains the espresso coffee grounds. It is then poured into the cup. The steam is able to create enough pressure to push the coffee grounds through. This creates a foam on top of the espresso. This is the hallmark of a great espresso.

There are three kinds of espresso makers, and they differ in the type of pump they employ and how hot the brew is. There are various ways that the brew can be controlled, as well as the size of the cup the machine is capable of making.

The first espresso machines were steam-type. They used one boiler to make both brew and steam, but the pressure they could create was minimal - two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. This is why the Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most commonly used espresso maker is a semiautomatic machine with an electric pump. These are the things people think of when they think of an espresso maker. With a semi-automatic espresso machine, you grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is a fantastic solution that combines human control with mechanised accuracy.

The Filter

Typically, espresso machines have filters that separate the coffee grounds as they pass through the hot water. The filter is also a vital element of the machine's temperature control, since it helps to prevent overheating.

A filter can also help with flavor as it allows for an extended flowering time. This lets the beans let their nuances out, and also allows for better extraction.

It is important to remember that even the finest filter can result in a bad cup of coffee. The quality of the beans as well as the extraction, are still very important.

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

In the steam-driven espresso machine hot water is heated in an airtight container to create steam, which then pushes the hot water through the grounds at high pressure. These kinds of machines are usually less expensive and easier to maintain than pump-driven models. They are however limited for creating the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

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