How Does Machine Espresso Work?

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

Espresso is produced by pushing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.

The Group Head

The name implies, the group head is the place you insert your portafilter when making espresso. 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 its own advantages and drawbacks. Some are focused on temperature stability, others on pre-infusion options, and others are designed to control the lever. Some come with a combination of both, like the E61. This is a popular choice among baristas because it offers multiple advantages in a single package.

As you can see in the image above the group head comes with many notches in which you can place your portafilter and then twist it manually to lock it in. There is also a gasket made of rubber in the notches, which helps create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for a precise placement of the portafilter, which is vital to ensure an efficient extraction.

Aside from allowing you to easily place your portafilter in, the group head is also responsible to ensure that the temperature remains even. It does this by circulating hot water through the brew basket and around the portafilter, making sure that it is always at the right temperature to extract. It is important to note that even a small deviation can make the difference between a decent and a excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, Rotary espresso machines rely on motorized pumps bean to cup espresso machines (additional reading) supply 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 being pumped through the ground coffee in the group head.

Pumps are typically more affordable and last longer than piston-driven machines. However, both types of machines may degrade because of frequent use and inadequate cleaning. They also make mechanically complex which can result in costly prices for even the most basic models.

Certain espresso machines remove the pump completely and instead employ steam pressure to create espresso maker barista. This can cause over-extraction because the boiler that makes steam also warms the water to boil. Additionally the machines often have to restore their pressure between cups, which takes time and energy.

A large majority of espresso machines employ the rotary or vibration pump. A vibration model employs a rotating disk to generate pressure, while a rotating model pushes hot water through the ground at a high speed. Both models are capable of producing excellent espresso and filter coffee machine, but rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is what heats the water to the ideal temperature to extract. The steam that is created gets to the portafilter which is a container for espresso grounds. It is then pumped into the cup. The steam creates pressure to push through the grounds of the coffee. This creates a foam on top of the espresso. This is one of the hallmarks of a great espresso.

There are three kinds of espresso machines, each with different pumps and brew temperature. There are also different ways that the brew may be controlled as well as the size of the cup that the maker can create.

The earliest espresso machines were steam-based. They used one boiler to create both steam and brew, however, the pressure they could generate was low - only 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 popular espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they imagine these machines. If you have a semi-automatic machine you must grind the beans and then tamp them by hand. However, the pump provides regulated water flow and pressure. This is a great compromise between human control and mechanized accuracy.

The Filter

Typically, espresso machines have a filter to separate out the coffee grounds as they pass through the hot water. The filter is also an important component of the temperature control system as it prevents the machine from overheating.

Filters also aid in flavor because it allows for an extended flowering time. This allows beans to let their nuances out and provides an opportunity to improve extraction.

It is important to keep in mind that even the most efficient filter could result in a poor cup of coffee. The quality of the beans as well as the extraction, are still very important.

It's here that the magic occurs. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you use to put the grounds of your coffee into when making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to produce steam. The steam then moves hot water through the coffee grounds under high pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability to create 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 been gaining popularity. They utilize an air compressor to force hot water through the ground and are much more mobile than steam-driven electric espresso machines.