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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to create the coffee we love. What exactly does it work?

Espresso is made by forcing 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 Group Head

The group head is the portafilter you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter, and controlling the pressure that results from the extraction. There are several different types of group heads each with its unique 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 popular choice among baristas since it provides multiple advantages in a single package.

As you can see in the above photo, the group head has several notches to place your portafilter and twist it manually to lock it in. There is also a gasket made of rubber in the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches permit the precise placement of the portafilter. This is essential for an accurate extraction.

In addition to allowing you easily place your portafilter in, the group head is responsible to maintain an even temperature. It does this by circulating hot water through the brew container and around the portafilter, making sure that it is always at the correct temperature for extraction. This is crucial, since just a few degrees could be the difference between a good and excellent espresso.

The Pump

Motorized pumps in rotary espresso machines supply the nine atmospheric bars of pressure required for espresso extraction. This is different from manually operated piston machines that employ levers. The pressure builds by drawing tap water from a reservoir and pumping it through a heat exchanger before being shot through the ground coffee inside the group head.

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

Certain espresso machines eliminate the pump entirely and make use of steam pressure to make espresso. The drawback is that the boiler that produces steam also raises the temperature of water until it reaches boiling which can cause over-extraction. Additionally these machines typically have to restore their pressure between cups, which requires time and energy.

A large majority of espresso machines employ a rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, while the Rotary model pushes hot coffee through the ground at a high speed. Both machines produce great espresso but rotary machines are more stable, quieter and less likely to break down.

The Boiler

The boiler is the part that heats the water to the ideal temperature for extraction. The resultant steam then reaches the portafilter that contains the ground espresso coffee, and is then funneled down into the cup. During this process, the steam creates pressure that pushes through the grounds of the coffee. This results in a crema on top of the espresso. This is the hallmark of a great espresso.

There are three kinds of espresso makers, which differ in the type of pump they use and how hot the brew is. There are various ways that the brew can be controlled as well as the dimensions of the cup the machine is capable of making.

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

The most well-known espresso machine is a semiautomatic that has an electric pump. These are what people imagine when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the flow of water and pressure. This is a perfect solution that combines human control with mechanized consistency.

The Filter

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

A filter also improves flavor as it allows for a longer flowering period. This allows the beans to release their nuances, and also allows for better extraction.

However, it is important to remember that even a great filter could result in a bad cup of coffee, because the quality of the beans and extraction are important.

This is where the magic happens, it's what makes espresso taste good. The grouphead (also called the brewhead) is where you put the portafilter, the thingy that you use to put the grounds of your coffee into when making espresso.

In the steam-driven espresso machine hot water is heated in an airtight tank to create steam. Steam then pushes the hot water through the grounds with high pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the perfect conditions for brewing, since they operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar.

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