How Does Machine Espresso Work?

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

Espresso is produced by pushing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee. However, the pressure is the major difference.

The Head of the Group

As the name implies, the group head is the place you put your portafilter in when brewing espresso. It disperses water in the portafilter, and regulates the pressure during the extraction. There are a variety of group heads each with distinct advantages and drawbacks. Some are focused on temperature stability, whereas others on pre-infusion capabilities, and Machine Espresso still others are designed to control the lever. Some have a combination, like the E61. This is a very popular choice for baristas because it offers multiple benefits in one package.

As you can see from the picture above the group head is equipped with several notches. It is possible to place your portafilter into these notches and turn the head around to secure it. A gasket made of rubber is placed within the notches to make a seal when you insert your portafilter. The notches allow for precise placement of your portafilter. This is essential for an accurate extraction.

Aside from 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, ensuring that it's always at the correct temperature to extract. This is important because just a few degrees could mean the difference between good and great espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to deliver the nine atmospheric bars of pressure needed for espresso extraction. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.

Pumps are typically less expensive and last longer than piston-driven machines. However, both kinds of machines may degrade because of frequent use and insufficient cleaning. They also increase the complexity of mechanical systems, which can result in the cost of even the simplest models.

Certain espresso machines can eliminate the pump completely and instead use steam pressure to brew espresso. This can cause over-extraction because the boiler that makes steam also heats the water until it comes to a boil. Additionally these machines typically have to rebuild their pressure between cups, which takes time and energy.

A majority of espresso machines use a vibration or rotary pump, which is a vibration model that uses a vibrating disc to generate the pressure and the rotary model pushing hot water through the grounds under high speed. Both types of machine are capable of producing excellent espresso, however the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is what heats the water to the perfect temperature for extraction. The resulting steam is then transferred to the portafilter which holds the ground espresso and is then funneled down into the cup. The steam causes pressure to push through the coffee grounds. This results in a layer crema that is then poured over. This is one of the main characteristics of a great espresso.

There are three distinct types of espresso machines, each with a different type of pump and the temperature of the brew. 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 earliest espresso machines were steam type. The first espresso machines were steam-type machines. This led to the coffee tasting burnt and bitter. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso machine is a semiautomatic model with an electric pump. These are the images people have when they think of an espresso maker. With a semi-automatic espresso machine, you have to grind the beans and then tamp them yourself but the pump regulates the flow of water and pressure. This is an excellent compromise between human touch and mechanized quality.

The Filter

Typically, espresso machines utilize filters to separate the grounds of coffee as they move through the hot water. The filter is also an important element of the temperature control system, as it keeps the machine from overheating.

A filter also helps with flavor because it allows for an extended flowering time. This allows the beans to release their flavor and also allows for better extraction.

It is important to remember that even the finest filter can produce a bad cup of coffee. The quality of the beans and the extraction, remain crucial.

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

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to create steam. The steam then pushes hot water into the grounds of coffee under high pressure. These kinds of machines are generally cheaper and easier to maintain than pump-driven models. They are however limited in their ability to create the perfect conditions for brewing since they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to push the hot water through the grounds and are significantly more portable than electric steam-driven machines.