How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and mind-blowing filter technology to make the perfect cup of coffee. But how exactly does it work?

Espresso is made by forcing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee however the main difference lies in the pressure.

The Group Head

The group head is the portafilter you put in when making espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the extraction. There are several different types of group heads, each with their distinct advantages and disadvantages. Some are designed for temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. Some contain a variety of features, like the E61, which is considered the standard choice for many baristas due to its capacity to offer multiple perks in one package.

As you can see in the above photo the head of the group is fitted with a variety of notches. It is possible to place your portafilter into these notches and twist the head to secure it. There is also a rubber gasket in the notches and helps create an airtight seal after inserting your portafilter into the machine. The notches allow for precise placement of the portafilter. This is essential for a consistent extraction.

Aside from allowing you to easily place your portafilter in, the group head is also responsible for maintaining a consistent temperature. This is done by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is constant for extraction. It is important to remember that even a slight deviation can make the difference between a decent and a excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger before being shot through the ground coffee in the group head.

Pumps tend to be cheaper than piston-driven machines and tend to last longer, although both types of machines may degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, and can add to the price of even the simple models.

Certain espresso machines can eliminate the pump completely and instead make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that makes steam also heats the water to boil. Additionally these machines typically have to rebuild their pressure between cups, which takes time and energy.

A majority of espresso machines use a vibration or rotary pump, which has a vibration model that uses a vibrating disc that generates the pressure and the rotary model pushing hot water through the grounds at high speed. Both machines can make great espresso, but rotary machines are more stable, quieter and less likely to fail.

The Boiler

The boiler is what will heat the water to a temperature that is ideal for extraction. The resultant steam then reaches the portafilter that contains the ground espresso coffee and is then funneled down into the cup. During this process, steam causes pressure to push through the coffee machines espresso grounds. This produces a layer of crema that is then poured over. This is a hallmark of a good espresso.

There are three distinct types of espresso machines, each with different pumps and the temperature of the brew. There are different ways to control the brew and the size of the cup that can be made by the machine.

The first espresso machines were steam-types. The first espresso machines were steam types. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso maker is a semi-automatic one that has an electric pump. This is what people envision when they think of an espresso machine. With a semi-automatic espresso machine, you grind the beans and tamp them by hand, but the pump regulates the flow of water and pressure. This is an excellent compromise between human touch and mechanized quality.

The Filter

Espresso machines typically use filters that separate the coffee grounds from the hot water. The filter is also a vital component of the machine’s temperature control, as it prevents overheating.

It also improves flavor as a filter allows for a longer bloom phase. This allows the beans to let their nuances out and provides the chance for better extraction.

It is important to keep in mind that even the Best Bean To Cup Espresso Machine filter can result in a bad cup of coffee. The quality of the beans, and the extraction, are still very important.

This is where the magic happens, it’s the thing that makes an espresso really taste great. The grouphead, sometimes called the brew head, is where the portafilter (the thingy you put the coffee grounds into) is placed when you’re making espresso.

Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water through grounds of coffee at high pressure. These kinds of machines are generally less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to provide the ideal brewing conditions, since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.

In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They make use of an air compressor to force hot water through the ground and are much more mobile than steam-driven electric espresso machines.