How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and incredible filter technology to produce the delicious coffee we enjoy. How exactly does it work?

In order to make espresso coffee machine, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee, but the difference is in the pressure.

The Group Head

As the name implies the group head is where you insert your portafilter when brewing espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the extraction. There are a variety of group heads each with its own advantages and disadvantages. Some are designed to provide the stability of temperature while some are specifically designed to handle pre-infusion. Others are built to control the lever. There are some that include a mix of features, such as the E61 that is the standard choice for many baristas due to its ability to offer multiple benefits in one package.

As you can see from the above photo the group head is fitted with a variety of notches. You can place your portafilter in these notches, then twist the head to secure it. There is also a gasket made of rubber which is located inside the notches and helps to create a seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is essential for an even extraction.

Aside from allowing you to easily insert your portafilter, the group head is also responsible for maintaining a consistent temperature. This is accomplished by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is constant to extract the coffee espresso machine. This is crucial, since just a few degrees could be the difference between a excellent and great espresso.

The Pump

Contrary to manual piston machines which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the ground coffee inside the group head.

Pumps tend to be cheaper than piston-driven machines, and they tend to last longer. However, both types of machine can get damaged through overuse and lack of cleaning. They also create mechanical complexity that can lead to costly prices for even the most basic models.

Some espresso machines eliminate the pump entirely and employ steam pressure to create espresso coffee machines. This could lead to over-extraction since the boiler that produces steam also heats the water until it comes to a boil. Additionally, these machines frequently have to rebuild their pressure between cups, which requires time and energy.

A large majority of espresso machines employ the rotary or vibration pump. A vibration model uses a rotating disk to generate pressure, whereas a rotary model pushes hot water through the ground at a rapid 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 used to heat the water to the ideal temperature for extraction. The steam that is produced gets to the portafilter which is a container for espresso grounds. It is then poured into the cup. The steam generates enough pressure to push the grounds of coffee through. This results in a whipped-up the top of the espresso. This is a sign of a great espresso.

There are three kinds of espresso machines, each having a different type of pump and the temperature of the brew. There are different ways in which the brew can be controlled and the size of the cup the machine is capable of making.

The first espresso machines were steam-types. They utilized a single boiler to make steam and brew, however the pressure they were able to produce was very low - just two bars of atmospheric pressure at most. The coffee tasted bitter and burned. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most common espresso machine is a semiautomatic one with an electric pump. When people think of buy espresso machine machines, they picture these machines. With a semi-automatic espresso machine, you have to grind the beans and tamp them by hand. However, the pump provides regulated water flow and pressure. This is an excellent compromise between human touch and the mechanized quality.

The Filter

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

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

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

This is where the magic happens, it's the thing that makes espresso taste great. The grouphead, also referred to as the brew head, is the place where the portafilter (the thing you put the coffee grounds into) is located when you're making espresso.

Steam-driven cheap espresso machine machines use hot water that is heated in an airtight container to create steam. The steam then moves hot water through the grounds of coffee at high pressure. These kinds of machines are usually less expensive and simpler to maintain than pumps-driven models. They are however limited in their ability for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

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