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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to make the perfect cup of coffee. How exactly does it work?

Espresso is made by forcing hot water at high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.

The Group Head

The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing the water into the portafilter and then controlling the pressure that results from the extraction. There are many different kinds of group heads, each with their distinct advantages and disadvantages. Some are specifically designed for temperature stability while others are built to handle pre-infusion. Others are built to control the lever. Some include a combination such as the E61. This is a popular choice among baristas because it offers multiple benefits in a single package.

As you can see in the above photo the group head is made up of numerous notches that you can put your portafilter, then twist it with your hands to lock it in. There is also a gasket of rubber which is located inside the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches allow for precise placement of your portafilter. This is crucial for a consistent extraction.

The group head not only lets you to place your portafilter easily however it also keeps a constant temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket, ensuring the temperature is always right to extract the coffee. This is vital, because even a few degrees can make the difference between a good and excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure needed to extract espresso. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pumped through the ground coffee inside the group head.

Pumps tend to be cheaper and last longer than piston-driven machines. However, both kinds of machines can degrade due to excessive use and insufficient cleaning. Pumps are also more complex mechanically, and can add to the cost of even simplest models.

Some espresso machines do away with the pump entirely and use steam pressure to brew espresso. This can result in over-extraction because the boiler that produces steam also causes the water to boil. The machines must also continually rebuild their pressure between cups. This takes energy and time.

Many espresso machines use the rotary or vibration pump. A vibration model makes use of an oscillating disk to create pressure, whereas the rotating model pushes hot water through the ground at a high speed. Both types of machine can make a great espresso, however 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 to extract. The steam produced reaches the portafilter, which holds the espresso grounds. It is then funneled into the cup. The steam creates pressure that pushes through the coffee grounds. This results in a layer crema on top. This is a sign of a good espresso.

There are three kinds of professional espresso maker makers. They differ in the type of pump they employ and the degree of heat that the brew is. There are different ways to control the brew and the size of the cup that can be produced by the machine.

The first espresso machines were steam-based. They employed one boiler to make both brew and steam, however the pressure they were able to generate was low - only two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was invented by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso maker is a semiautomatic machine with an electric pump. This is what people envision when they think of an Espresso Coffee Machine Home machine. Semi-automatic machines require you to grind and tamp your beans yourself, but the pump regulates the flow of water and pressure. This is an excellent solution that combines human control with mechanized consistency.

The Filter

Espresso machines typically have filters that separate the coffee grounds from the hot water. The filter is also a vital component of the machine's temperature control, since it stops overheating.

A filter can also help with flavor because it allows for an extended flowering time. This allows the beans to release their flavor and improves extraction.

However, it is important to remember that even a great filter can produce a bad cup of coffee, as the quality of the beans and extraction is vital.

It's here that the magic happens. This is the reason why espresso tastes so good. The grouphead, sometimes referred to as the brewhead, is where the portafilter (the device you put the coffee grounds into) sits when you're making espresso.

Steam-driven espresso machines make use of hot water heated in an airtight container to produce steam. The steam then moves hot water through the grounds of the coffee under pressure. They are less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to create the ideal brewing conditions, since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.

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