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How Does Machine Espresso Work?

The machine espresso uses precision pressure, and a filter technology that is awe-inspiring to create the coffee you enjoy. But 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 the pressure is the primary difference.

The Group Head

The group head is the portafilter you place in the espresso maker when making it. It distributes water into the portafilter, and regulates the pressure of the extraction. There are a variety of types of group heads, each with their particular advantages and drawbacks. Some are designed to provide stability of temperature while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some contain a variety of features, such as the E61, which is considered to be the most popular among baristas due to its ability to provide multiple benefits in a single package.

As you can see in the above image the group head is made up of numerous notches that you can put your portafilter, then twist it manually to lock it in. There is also a gasket made of rubber that is a part of the notches to help create an airtight seal when you insert your portafilter into the machine. The notches allow for precise placement of your portafilter. This is essential for an accurate extraction.

The group head not only allows the portafilter to be inserted easily, but it also maintains an even temperature. This is done by cycling hot water around the portafilter, and through the brew-basket to ensure the temperature is always right for extraction. It is important to note that even a slight variation can mean the difference between a good and a great espresso.

The Pump

In contrast to manual piston machines which rely on a lever that pressurize water, the rotary best budget espresso machine machines use motorized pumps that provide the nine atmospheric bars of pressure required to extract espresso. The pressure is created by drawing tap water from a reservoir and pumping it through a heat exchanger before it is shot through the ground coffee inside the group head.

Pumps tend to be less expensive than piston-driven models, and they tend to last longer, although both types of machines may get damaged through overuse and lack of cleaning. They also increase the complexity of mechanical systems which can result in an expensive price for even the most basic models.

Some espresso machines make use of steam pressure instead of a pump for brewing espresso. This can cause over-extraction because the boiler that makes steam also heats the water to boil. In addition these machines typically have to rebuild their pressure between cups, which requires time and energy.

A majority of espresso machines use either a rotary or vibration pump, which is a vibration model using a rotating disc to generate the pressure and rotating models that push hot water through the grounds at high speed. Both types of machine can produce an excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the element which heats the water to the optimal temperature to extract. The steam produced reaches the portafilter, which is the container that holds the espresso maker for home coffee grounds. The steam is then channeled into the cup. The steam causes enough pressure to push the grounds of the coffee through. This results in a layer of crema on top. This is one of the main characteristics of a great espresso home machine.

There are three types of espresso makers, and they differ in the kind of pump they use and the degree of heat that the brew is. There are a variety of ways in which the brew could be controlled as well as the size of the cup the machine is capable of making.

The first espresso machines were steam-type. They employed a single boiler to make both brew and steam, but the pressure they could create was minimal - two bars of atmospheric pressure maximum. The coffee tasted bitter and burned. The modern espresso machine was designed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they think of these machines. Semi-automatic machines require you to grind and tamp the beans by yourself while the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanized accuracy.

The Filter

Espresso machines typically use filters that separate the grounds of coffee from hot water. The filter is also a crucial component of the temperature control system, because it stops the machine from overheating.

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

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

It's in this area that the magic occurs. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you place the portafilter, the thingy which you put the coffee grounds in, when making espresso.

Steam-driven espresso machine with grinder machines make use of hot water heated in an airtight container to produce steam. The steam then pushes hot water through coffee grounds under high pressure. These kinds of machines are typically less expensive and easier to maintain than pump-driven models. They are however limited in their ability for creating the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

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