How Does Machine Espresso Work?

Machine espresso employs precise pressure and amazing filter technology to make the coffee we love. How exactly does it work?

To make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the primary difference.

The Group Head

As the name implies the group head is the place you place your portafilter while brewing espresso. It distributes water into the portafilter, and regulates the pressure of the extraction. There are many different kinds of group head, each with their particular advantages and drawbacks. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Some are designed to control the lever. Some include a combination like the E61. This is a preferred choice for baristas as it provides a variety of benefits in a single package.

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

In addition to allowing you to easily place your portafilter in, the group head is responsible to maintain an even temperature. This is accomplished by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is constant for extraction. It is important to realize that even a small variation can mean the difference between a good and a great espresso.

The Pump

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

Pumps tend to be cheaper than piston-driven models, and they tend to last longer, however both types of machines can degrade with overuse and insufficient cleaning. Pumps are also more complex mechanically, which could increase the cost of even the simplest models.

Some espresso machines can eliminate the pump completely and use steam pressure to brew espresso. This can lead to over-extraction as the boiler that makes steam also heats the water to boil. In addition these machines are often required to restore their pressure between cups, which takes time and energy.

Many espresso machines make use of a rotary or vibration pump. A vibration model utilizes the vibrating disk to create pressure, whereas a circular model pushes hot liquid through the ground at a high speed. Both models can produce an excellent espresso, however the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is the part which heats the water to the optimal temperature for extraction. The resulting steam is then transferred to the portafilter containing ground espresso beans and is then funneled down into the cup. In this process, the steam creates pressure that pushes through the coffee grounds. This creates a crema on top of the espresso. This is the hallmark of a great espresso.

There are three types of espresso makers. They differ in the type of pump they use and the degree of heat that the espresso is. There are different ways that the brew may be controlled as well as the dimensions of the cup the maker can create.

The first espresso machines were steam-type. The earliest espresso machines were steam types. This led to the coffee tasting burnt and bitter. The modern espresso machine was developed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso machine is a semiautomatic one with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic espresso machine, you grind the beans and then tamp them by hand, but 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 usually have filters that separate the grounds of the coffee from the hot water. The filter is also a vital component of the temperature control system, because it stops the machine from overheating.

It also aids in flavor, as it allows for a longer bloom time. This allows the beans to release their flavor and improves extraction.

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

It's here that the magic takes place. This is what makes espresso taste so good. The grouphead (also called the brewhead) is where you place the portafilter - the thingy that you use to put the grounds of coffee into when making best home espresso machine.

Steam-driven espresso machines use hot water heated in an airtight container to produce steam. The steam then pushes hot water through grounds of the coffee under pressure. These types of machines tend to be less expensive and easier to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bars.

In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They utilize an air compressor to force the hot water through the grounds and are much more portable than steam-driven electric machines.