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How Does Machine Espresso Work?

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

To make an espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure.

The Head of the Group

The group head is the portafilter that is inserted when you are making espresso. It disperses water into the portafilter and regulates the pressure of the extraction. There are numerous kinds of group heads, each with its own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. Some have a combination, such as the E61. This is a favorite among baristas since it provides multiple advantages in a single package.

As you can see in the above image the group head comes with several notches to put your portafilter, then twist it manually to lock it in. There is also a gasket of rubber which is located inside the notches and 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 for maintaining an even temperature. This is done by cycling hot water around the portafilter and through the brew basin, ensuring that the temperature is always at the right level to extract the coffee. This is important because even a small difference in temperature can be the difference between a excellent and great espresso capsule machine.

The Pump

The motorized pumps that are used in espresso machines rotary provide nine atmospheric bars of pressure required to extract espresso. This is different from manual piston machines that use levers. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally less expensive than piston-driven models, and they tend to last longer. However, both types of machines could become damaged due to excessive use and poor cleaning. They also create mechanical complexity that can lead to the cost of even the simplest models.

Some espresso machines make use of steam pressure instead of a pump to brew espresso machines for home. The drawback is that the same boiler that produces steam also raises the temperature of the water until it reaches boiling which can cause excessive extraction. Additionally these machines are often required to rebuild their pressure between cups, which requires time and energy.

Many espresso machines make use of an rotary or vibrating pump, which has a vibration model using a vibrating disc to create the pressure, and an rotary model that pushes hot water through the grounds under high speed. Both machines can make great espresso however rotary machines tend to be more quiet, durable and less likely to break down.

The Boiler

The boiler is used to heat the water to the perfect temperature for extraction. The steam that is produced reaches the portafilter which holds ground espresso beans and is then funneled down into the cup. During this process the steam creates enough pressure to push the coffee grounds through. This produces a layer of crema that is then poured over. This is the hallmark of a good buy espresso machine.

There are three kinds of espresso makers. They differ in the type of pump they use and how hot the brew is. There are different ways in which the brew could be controlled and the size of the cup the maker can create.

The first espresso machines were steam-types. They employed one boiler to make both steam and brew but the pressure they could create was minimal - two bars of atmospheric pressure, at most. This resulted in the coffee tasting burnt and bitter. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most popular espresso machine is a semiautomatic with an electric pump. This is what people envision when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is a great compromise between human control and mechanized reliability.

The Filter

Typically, espresso machines have a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also an essential component of the machine's temp control, as it helps prevent overheating.

A filter also helps with flavor since it allows for the beans to flower for a longer period of time. This lets the beans release their flavors, and allows for better extraction.

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

This is where the magic happens. It's what makes espresso taste good. The grouphead (also called the brewhead) is where you place the portafilter - the thingy that you put the coffee grounds in, when making espresso.

Steam-driven espresso machines use hot water heated in an airtight vessel to create steam. The steam then pushes hot water through the grounds of coffee at high end espresso machine 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 perfect conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

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