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How Does Machine Espresso Work?

machine espresso (Douerdun published a blog post) uses precision pressure and amazing filter technology to make the delicious coffee we enjoy. What exactly does it work?

Espresso is made by pushing hot water under high pressure through finely-ground coffee. The process is similar to making drip coffee for espresso machine. However, the pressure is the major difference.

The Head of the Group

The group head is the portafilter that you place in the espresso maker when making it. It disperses water in the portafilter, and regulates the pressure of extraction. There are many different types of group heads, each with its own advantages and disadvantages. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Others are built to control the lever. Some have a combination, such as the E61. This is a very popular choice for baristas since it provides multiple benefits in a single package.

As you can see in the above image the group head comes with several notches where you place your portafilter and twist it with your hands to secure it. There is also a gasket made from rubber that resides inside the notches, which helps create an airtight seal when you insert your portafilter into the machine. The notches allow for precise placement of the portafilter. This is essential for an accurate extraction.

Aside from allowing you to effortlessly insert your portafilter the group head is also responsible to ensure that the temperature remains even. It does this by cycling hot water through the brew basket and around the portafilter to ensure that it's always at the right temperature to extract. It is important to realize that even a few degree difference can make the difference between a good and a excellent espresso.

The Pump

Unlike manual piston machines, which use a lever to pressurize water, the rotary espresso machines use motorized pumps to provide the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by removing 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 less expensive and last for longer than piston-driven machines. However, both types of machines may degrade due to excessive use and inadequate cleaning. Pumps are also more complex mechanically, which can raise the price of even the most basic models.

Some espresso machines use steam pressure instead of a pump to make espresso. The downside is that the boiler that produces steam also increases the temperature of water to the point of boiling and can result in over-extraction. These machines also have to continually rebuild their pressure between cups. This takes energy and Machine Espresso time.

A large majority of espresso machines employ an rotary or a vibration pump. A vibration model uses an oscillating disk to create pressure, whereas a circular model pushes hot liquid through the ground at a fast speed. Both types of machine are capable of producing excellent espresso, but Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The dual boiler espresso machine is the part that heats the water to the optimal temperature to extract. The steam that is produced reaches the portafilter which holds the ground espresso and gets funnelled down into the cup. During this process the steam generates enough pressure to push the coffee grounds through. This creates a foam on the top of the espresso. This is one of the main characteristics of a good espresso.

There are three different types of espresso machines, each having different pumps 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 produced by the machine.

The first espresso machines were steam-types. They had 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 the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most common espresso machine is a semiautomatic with an electric pump. These are the images people have when they think of an espresso maker. With a semi-automatic espresso machine, you need to grind the beans and tamp them yourself but the pump is able to regulate the flow of water and pressure. This is a perfect combination of human control and mechanised reliability.

The Filter

Espresso machines usually have a filter that separates the grounds of the coffee from the hot water. The filter is also an essential component of the temperature control system, because it stops the machine from overheating.

A filter also improves flavor, as it permits an extended flowering time. This helps the beans to let their nuances out and provides an opportunity for better extraction.

It is important to keep in mind that even the best filter can result in a bad cup of coffee. The quality of the beans, and the extraction process, are still very important.

This is where the magic happens, it's what makes espresso taste great. The grouphead (also called the brewhead) is where you put the portafilter - the thingy used to place the coffee grounds in, when making espresso.

In a steam-driven travel espresso maker machine, hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds with high pressure. These types of machines are usually less expensive and easier 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 ideal shot requires 9-10 bars.

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