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?

In order to make espresso hot water is pushed under 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

The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing water into the portafilter before controlling the pressure of the resulting extraction. There are a variety of types of group heads each with its particular advantages and disadvantages. Some are designed for stability of temperature while others are built to handle pre-infusion. Some are designed to control the lever. Some are a combination, like the E61. This is a preferred choice for baristas as it provides a variety of benefits in a single package.

As you can see in the photo above the group head is fitted with a variety of notches. You can place your portafilter inside these notches, and then twist the head to lock it. There is also a gasket made of rubber that resides inside the notches, which helps create the seal when you insert your portafilter into the machine. The notches on the head permit a precise location of the portafilter which is crucial for an efficient extraction.

The group head not only allows you to insert your portafilter easily however it also keeps an even temperature. This is achieved by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is constant for extraction. This is important, as even a small difference in temperature can mean the difference between good and great espresso.

The Pump

Motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure required for espresso extraction. This is different 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 less expensive than piston-driven models, and they tend to last longer, however both types of machines can get damaged through overuse and lack of cleaning. They also make mechanically complex that can lead to the cost of even the most basic models.

Some espresso machines employ steam pressure instead of a pump to make espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of the water until it reaches boiling which could lead to excessive extraction. They also have to continuously rebuild their pressure between cups. This requires energy and time.

A large majority of espresso machines employ either a vibration or rotary pump. A vibration model utilizes a vibrating disk to generate pressure, while a circular model pushes hot liquid through the ground at high speed. Both types of machines are capable of producing excellent espresso, but rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is what heats the water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter containing the ground espresso and gets funnelled down into the cup. The steam causes enough pressure to push the grounds of coffee through. This results in a layer crema that is then poured over. This is one of the hallmarks of a great espresso.

There are three kinds of espresso makers. They differ in the kind of pump they use and how hot the coffee is. There are different ways that the brew may be controlled, as well as the dimensions of the cup the machine can make.

The first espresso machines were steam-type. The earliest espresso machines were steam-type machines. This led to the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso maker is a semiautomatic machine that has an electric pump. This is what people envision when they think of an espresso maker. With a semi-automatic machine, you need to grind the beans and then tamp them by hand. The pump controls the flow of water and pressure. This is a great compromise between the human touch and mechanized consistency.

The Filter

Typically, espresso machines utilize filters to separate the coffee grounds as they pass 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 aids in flavor, as a filter lets you enjoy a longer bloom phase. This allows the beans to let their nuances out, and also allows for better extraction.

However, it is important to remember that even a high-quality filter could result in a bad cup of coffee, because the quality of the beans and extraction are essential.

This is where the magic happens, and it's what makes espresso taste great. The grouphead, also called the brewhead, is where the portafilter (the thingy you put the coffee grounds into) sits when you're making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight tank to create steam. Steam then pushes the hot water through the grounds under high pressure. These types of machines tend to be less expensive and simpler to maintain than pump-driven models. However, they are limited in their ability to produce the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.

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