How Does Machine Espresso Work?

The machine espresso is made using precision pressure, and filter technology that is mind-blowing to make the coffee you enjoy. How exactly does it work?

In order to make 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 primary difference.

The Group Head

The group head is the portafilter you place in the professional espresso machine for home maker when making it. It is responsible for dispersing the water into the portafilter and then controlling the pressure that results from the extraction. There are many different types of group heads each with distinct advantages and disadvantages. Some focus on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. Some include a mix of features, such as the E61 that is the most popular choice among baristas for its ability to offer multiple perks in a single package.

As you can see in the photo above the group head comes with many notches in which you can place your portafilter and twist it with your hands to lock it in. A gasket made of rubber is positioned inside the notches, which helps make a seal when you insert your portafilter. The notches on the head permit a precise position of the portafilter which is vital for an even extraction.

In addition to allowing you easily connect your portafilter, the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket, and around the portafilter, ensuring that it's always at the correct temperature for extraction. It is important to realize that even a slight variation can mean the difference between a good and excellent espresso.

The Pump

Unlike manual piston machines, which rely on a lever to pressurize water, rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure necessary to extract espresso. The pressure is created by drawing tap water from a reservoir and pumping it through a heat exchanger before 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 can become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, which can increase prices of even simple models.

Some espresso machines do away with the pump entirely and utilize steam pressure to make espresso. The disadvantage of this is that the same boiler that produces steam also increases the temperature of the water to boiling, which can lead to excessive extraction. These machines also have to constantly rebuild their pressure in between cups. This requires energy and time.

A majority of espresso machines utilize an rotary or a vibration pump. A vibration model utilizes a vibrating disk to generate pressure, while the Rotary model pushes hot coffee through the ground at a rapid speed. Both machines can make great espresso machines home but rotary machines are more stable, quieter and less likely to break down.

The Boiler

The boiler makes the water warm to the perfect temperature for extraction. The steam created will eventually reach the portafilter, which contains the espresso maker barista coffee grounds. It is then pumped into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This results in a crema on the top of the espresso. This is a hallmark of a good espresso.

There are three types of espresso makers. They differ in the type of pump they employ and the degree of heat that the brew is. There are a variety of ways to control the amount of brew, as well as the size of the cup that can be made by the machine.

The first espresso coffee makers machines were steam types. They utilized a single boiler to make both brew and steam, however the pressure they were able to generate was low - only two bars of atmospheric pressure at the most. This led to the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso maker is a semi-automatic device with an electric pump. These are the things people think of when they think of an espresso maker (had me going). Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the flow of water and pressure. This is a perfect solution that combines human control with mechanized consistency.

The Filter

Espresso machines usually have a filter that separates the coffee grounds from the hot water. The filter is also a vital component of the machine's temp control, since it stops overheating.

It also enhances flavor, since a filter allows for a longer bloom time. This helps the beans to release their flavor and gives an opportunity to improve extraction.

However, it is important to keep in mind that even a great filter could result in a bad cup of coffee, since the quality of the beans and extraction is still important.

It's here that the magic occurs. This is the reason why espresso tastes so good. The grouphead, also called the brewhead, is where the portafilter (the thing you put the ground coffee in) is located when you're making italian espresso machines.

In a steam-driven espresso machine hot water is heated in an airtight tank to create steam. This is then pushed through the grounds under high pressure. They are less expensive and easier to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the ideal conditions for brewing since they operate at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.

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