How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to make the delicious coffee we enjoy. How exactly does it work?

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

The Group Head

The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the resulting extraction. There are a variety of types of group head, each with their distinct advantages and disadvantages. Some are designed to provide stability of temperature while others are designed to handle pre-infusion. Others are made to control the lever. There are even some that come with a range of features, like the E61, which is the classic choice among many baristas because of its ability to provide multiple benefits in a single package.

As you can see in the above photo the head of the group is fitted with several notches. You can place your portafilter into these notches and twist the head to secure it. A rubber gasket is located in the notches to make a seal when you insert your portafilter. The notches allow for the precise placement of the portafilter. This is crucial to ensure an accurate extraction.

The group head not only allows the portafilter to be inserted easily however, it also keeps a constant temperature. It does this by circulating hot water through the brew container and around the portafilter, ensuring that it's always at the correct temperature for extraction. This is important, as even a small difference in temperature can mean the difference between excellent and great espresso machines home.

The Pump

In contrast to manual piston machines that use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure that are required for espresso extraction. This pressure builds up by removing 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 machines, and tend to last longer, although both types of machines could be damaged by excessive use and inadequate cleaning. They also add mechanical complexity, which can result in costly prices for even the most basic models.

Certain Espresso Machine black friday machines do away with the pump completely and instead use steam pressure to brew espresso. The drawback of this is that the same boiler that produces steam also raises the temperature of water to the point of boiling which can cause excessive extraction. They also have to constantly rebuild their pressuremp. These are the things people think of when they imagine an espresso machine. With a semi-automatic machine you have to grind the beans and then tamp them yourself but the pump provides regulated water flow and pressure. This is an excellent compromise between human touch and mechanized consistency.

The Filter

Typically, espresso machines employ filters that separate the grounds of coffee when they pass through the hot water. The filter is also a crucial element of the temperature control system, since it helps prevent the machine from overheating.

It also improves flavor, since a filter allows for a more prolonged bloom phase. This helps the beans to release their nuances and gives an opportunity to improve extraction.

It is important to keep in mind that even the most efficient filter can result in a bad cup of coffee. The quality of the beans, and the extraction, remain vital.

It's here that the magic happens. This is what makes espresso taste so delicious. The grouphead, also referred to as the brew head, is where the portafilter (the thing you put the ground coffee and espresso machine into) is placed when making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam. This is then pushed through the grounds at high pressure. They are less expensive and easier to maintain than pumps-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 much more portable than electric steam-driven machines.