How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. What exactly does it work?

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

The Head of the Group

The name implies, the group head is the place you insert your portafilter when brewing espresso. It is responsible for dispersing water into the portafilter and controlling the pressure that results from the extraction. There are many different kinds of group heads, each with their particular advantages and drawbacks. Some focus on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some have a combination, like the E61. This is a very popular choice for baristas as it provides a variety of benefits in a single package.

As you can see in the picture above, the group head is fitted with a variety of notches. You can place your portafilter inside these notches, and then twist the head to secure it. A gasket made of rubber is placed inside the notches to help create a seal when you insert your portafilter. The notches permit precise placement of the portafilter. This is crucial for an even extraction.

In addition to allowing you to easily place your portafilter in, the group head is also responsible for maintaining an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it's always at the correct temperature to extract. It is important to remember that even a slight differences can make the distinction between a decent espresso machine and a great espresso.

The Pump

The motorized pumps in rotary espresso machines supply the nine atmospheric bars of pressure required to extract espresso. This differs from manual piston machines that rely on levers. The pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being pushed through the ground coffee inside the group head.

Pumps are typically less expensive and last for longer than piston-driven machines. However, both kinds of machines may degrade due to excessive use and insufficient cleaning. Pumps are also more complex mechanically, which can raise the price of even the simple models.

Certain espresso machines utilize steam pressure instead of a pump 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 could lead to excessive extraction. The machines must also constantly rebuild their pressure in between cups. This takes energy and time.

A large majority of espresso machines employ either a vibration or rotary pump. A vibration model uses a vibrating disk to generate pressure, while a circular model pushes hot liquid through the ground at a rapid speed. Both Machines Espresso Machines can produce excellent espresso, however rotary machines are more stable, quieter and less likely to break.

The Boiler

The boiler makes the water warm to the ideal temperature to extract. The resultant steam then reaches the portafilter that contains the ground espresso and is then pumped into the cup. During this process, steam creates pressure to push through the coffee grounds. This produces a layer of crema on top. This is one of the main characteristics of a good espresso machine with grinder.

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

The first espresso machines were steam-based. They employed a single boiler to make both steam and brew but the pressure they could create was minimal - two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. The modern espresso machine was developed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans by yourself while the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanized quality.

The Filter

Espresso machines typically have a filter that separates the grounds of the coffee and espresso machine from hot water. The filter is also an important element of the temperature control system, as it prevents the machine from overheating.

A filter also improves flavor because it allows for the beans to flower for a longer period of time. This allows the beans to release their nuances and gives the chance for better extraction.

It is important to remember that even the most efficient filter could result in a poor cup of coffee. The quality of the beans, as well as the extraction, remain vital.

It's here that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you put the portafilter - the thingy that you put the coffee grounds into, when making espresso.

Steam-driven espresso machines make use of hot water heated in an airtight vessel to create steam. The steam then pushes hot water through the grounds of the coffee under pressure. These types of machines tend to be cheaper and easier to maintain than pump-driven models. However, they are limited in their ability to produce the ideal conditions for brewing as they only operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.

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