How Does Machine Espresso Work?

The machine espresso uses precise pressure and filter technology that is awe-inspiring to create the coffee you enjoy. What exactly does it work?

Espresso is created by forcing hot water at high pressure through finely ground coffee. The process is similar to making drip coffee but the difference is in the pressure.

The Head of the Group

The group head is the portafilter that you put in when making espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure of the resulting extraction. There are numerous kinds of group heads each with its own advantages and drawbacks. Some are focused on temperature stability, others on pre-infusion capabilities, while others are designed to control the lever. Some have a combination, such as the E61. This is a popular choice among baristas as it provides a variety of benefits in one package.

As you can see in the above image the group head is made up of several notches where you place your portafilter before twisting it by hand to lock it in. A gasket made of rubber is placed within the notches to create a seal when you insert your portafilter. The notches permit precise placement of the portafilter. This is vital for an accurate extraction.

In addition to allowing you to easily place your portafilter in, the group head is responsible for maintaining an even temperature. It does this by circulating hot water through the brew basket, and around the portafilter to ensure that it's always at the correct temperature to extract. This is crucial, since just a few degrees could make the difference between good and excellent espresso machines home.

The Pump

The motorized pumps that are used in rotary espresso machines provide the nine atmospheric bar pressure needed for espresso extraction. This differs from manual piston machines that use levers. The pressure is created by pumping water through a heat exchanger and then through the ground coffee.

Pumps tend to be cheaper than piston-driven machines, Espresso machines home and they tend to last longer, but both types of machines may become damaged due to excessive use and poor cleaning. They also add mechanical complexity which can result in an expensive price for even the simplest models.

Some espresso machines employ steam pressure instead of a pump to brew espresso. The drawback of this is that the boiler that produces steam also increases the temperature of water to the point of boiling and can result in excessive extraction. Additionally, these machines frequently have to rebuild their pressure between cups, which takes time and energy.

Many espresso machines use either a vibration or rotary pump. A vibration model uses the vibrating disk to create pressure, whereas the circular model pushes hot liquid through the ground at a rapid speed. Both machines can produce excellent espresso however rotary machines tend to be more quiet, durable and less likely to break down.

The Boiler

The boiler is the component that heats water to an optimal temperature for extraction. The resultant steam then reaches the portafilter, which contains ground espresso beans and gets funnelled down into the cup. In this process, the steam causes pressure to push through the grounds of the coffee. This creates a foam on the top espresso machines of the espresso. This is one of the hallmarks of a good espresso.

There are three types of espresso machines, each with a different type of pump and brew temperature. There are different ways to control the brew and the size of cup that can be produced by the machine.

The first espresso machines were steam-type. They utilized a single boiler to make both 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 burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most well-known espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they think of these machines. Semi-automatic machines require you to grind and tamp your beans yourself The pump, however, regulates the flow of water and pressure. This is a great solution that combines human control with mechanized reliability.

The Filter

Typically, espresso machines employ a filter to separate out the grounds of coffee as they move through the hot water. The filter is also an essential part of the machine's temperature control, since it stops overheating.

A filter also improves flavor because it allows for a longer flowering period. This helps the beans let their nuances out and provides an opportunity to improve extraction.

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

This is where the magic happens. It's what makes an espresso really taste good. The grouphead, also referred to as the brewhead, is where the portafilter (the thingy you put the ground coffee into) is placed when making espresso.

In a steam-driven espresso machine hot water is heated in an airtight container to create steam. Steam is then pushed through the grounds under high pressure. These machines are cheaper and are easier for the user to maintain than pumps-driven models. However, espresso machines home they are limited in their ability to produce the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure. However, 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 significantly more portable than steam-driven electric machines.