How Does Machine Espresso Work?

The machine espresso uses precise pressure and filtering system that is awe-inspiring to make the coffee you enjoy. But how exactly does it work?

In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.

The Head of the Group

As the name suggests the group head is the place you insert your portafilter when making espresso. It disperses water in the portafilter, and regulates the pressure of extraction. There are many different kinds of group heads each with its particular advantages and disadvantages. Some are specifically designed for stability in temperature, while others are built to handle pre-infusion. Some are designed to control the lever. Some have a combination, such as the E61. This is a popular choice among baristas due to the fact that it has multiple benefits in a single package.

As you can see in the photo above the group head is equipped with several notches. You place your portafilter inside these notches, and then twist the head to lock it. A gasket of rubber is situated within the notches to create a seal when you insert your portafilter. The notches on the head allow for a precise position of the portafilter which is necessary to ensure a consistent extraction.

The group head not only lets you to put in your portafilter easily, but it also maintains the temperature at a constant level. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring the temperature is always right for extraction. It is important to note that even a few degree difference can make the difference between a good and great espresso.

The Pump

Unlike manual piston machines, which rely on a lever that pressurize water, Rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure necessary to extract espresso. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger before being pushed through the ground coffee in the group head.

Pumps are typically less expensive and last for longer than piston-driven machines. However, both kinds of machines can deteriorate due to overuse and poor cleaning. They also create mechanical complexity that can lead to a high price tag on even the most basic models.

Some commercial espresso machine machines can eliminate the pump completely and employ steam pressure to create espresso. This could lead to over-extraction since the boiler that produces steam also warms the water to boil. The machines must also continually rebuild their pressure between cups. This takes energy and time.

Many espresso machines use a rotary or vibration pump. A vibration model uses the vibrating disk to create pressure, whereas the rotating model pushes hot water through the ground at a fast speed. Both types of machine can make a great espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is what will heat the water to a temperature that is ideal for extraction. The resulting steam reaches the portafilter that contains the ground espresso coffee, and is then pumped down into the cup. During this process, the steam causes pressure to push through the coffee grounds. This creates a crema on the top of the espresso. This is a hallmark of a good espresso.

There are three types of italian espresso machine makers, which differ in the type of pump they employ and the degree of heat that the brew is. There are also different ways that the brew can be controlled, as well as the dimensions of the cup the machine can make.

The first espresso machines were steam-types. The first professional espresso machine machines were steam-type machines. This resulted in the coffee tasting burnt and bitter. The modern espresso machine was designed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso machine is a semiautomatic that has an electric pump. These are what people imagine when they think of an espresso maker. With a semi-automatic machine you grind the beans and then tamp them yourself but the pump is able to regulate the flow of water and pressure. This is an excellent compromise between human control and mechanized accuracy.

The Filter

Typically, espresso machines use filters that separate the grounds of coffee as they move through the hot water. The filter is also a vital part of the machine's temperature control, since it helps to prevent overheating.

It also helps with flavor as a filter lets you enjoy a longer bloom time. This allows beans to release their flavor and gives an opportunity to improve extraction.

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

This is where the magic happens, and it's what makes an espresso really taste good. The grouphead (also known as the brewhead) is where you put the portafilter, the device which you put the coffee machine espresso grounds into, while making espresso.

In the steam-driven espresso machine hot water is heated in an airtight tank to produce steam, which is then pushed through the grounds under high pressure. These machines are cheaper and easier for the owner to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

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