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How Does Machine Espresso Work?

The machine espresso is made using precision pressure, and a filter technology that is awe-inspiring to make the coffee you enjoy. How exactly does it work?

Espresso is created by forcing hot water under high pressure through finely-ground coffee. The process is similar to making drip coffee however the main difference lies 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 water into the portafilter and then controlling the pressure that results from the extraction. There are several different types of group head each with its distinct advantages and drawbacks. Some are focused on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. Some are a combination, such as the E61. This is a very popular choice for baristas due to the fact that it has multiple benefits in one package.

As you can see from the image above, the group head is fitted with several notches. You can place your portafilter in these notches and then twist the head to lock it. A gasket made of rubber is placed in the notches to create a seal when you insert your portafilter. The notches permit an exact placement of the portafilter. This is essential for an even extraction.

In addition to allowing you to easily insert your portafilter, the group head is responsible to ensure that the temperature remains even. This is achieved by cycling hot water around the portafilter and through the brew-basket to ensure that the temperature is always at the right level to extract the coffee. This is important, as just a few degrees could be the difference between a good and excellent espresso.

The Pump

Unlike manual piston machines, that use a lever to pressurize water, Rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure needed to extract espresso. This pressure is generated by pumping water through a heat exchanger and then through the ground coffee.

Pumps are generally more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and insufficient cleaning. Pumps are also more complex mechanically, which could increase prices of even simpler models.

Certain espresso machines can eliminate the pump completely and employ steam pressure to create espresso. The drawback is that the boiler that produces steam also raises the temperature of the water until it reaches boiling which could lead to over-extraction. These machines also have to constantly rebuild their pressure in between cups. This takes energy and time.

Many espresso machines make use of a rotary or vibration pump. A vibration model employs an oscillating disk to create pressure, whereas a rotating model pushes hot water through the ground at a high speed. Both machines can produce excellent espresso but rotary machines are more quiet, durable and less likely to break down.

The dual boiler espresso machine

The boiler is the element which heats the water to the ideal temperature for extraction. The resulting steam reaches the portafilter, which contains 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 results in a layer of crema on top. This is the hallmark of a good espresso.

There are three distinct types of espresso machines, each having different types of pumps and the temperature of the brew. There are different ways to control the brew and the size of cup that can be produced by the machine.

The first espresso machines were steam-based. They used a single boiler to make steam and brew, but the pressure they could create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most popular espresso maker is a semiautomatic machine with an electric pump. These are the images people have when they think of an espresso machine. With a semi-automatic espresso machine, you have to grind the beans and tamp them by hand, but the pump provides regulated water flow and pressure. This is a fantastic combination of human control and mechanised 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 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 allows for a better extraction.

It is important to keep in mind that even the most efficient filter can produce a bad cup of coffee. The quality of the beans, and the extraction process remain vital.

This is where the magic happens, and it's what makes an espresso really taste great. The grouphead, often called the brewhead, is where the portafilter (the device you put the ground coffee in) is placed when you're making espresso.

Steam-driven espresso maker barista machines use hot water that is heated inside an airtight container to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These kinds of machines tend to be cheaper and easier to maintain than pumps-driven models. However, they are limited in their capacity to create the ideal conditions for brewing as they only operate at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.

In recent years, compressed air-driven espresso machines have become more popular. They utilize an air compressor to force hot water into the ground and are more mobile than steam-driven electric espresso machines.