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How Does Machine Espresso Work?

Machine espresso employs precise pressure and amazing filter technology to make the perfect cup of coffee for espresso machine. What exactly is it that makes 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 Head of the Group

The group head is the portafilter you place in the espresso maker when making it. It disperses water into the portafilter, and regulates the pressure during the extraction. There are numerous kinds of group heads, each with its own advantages and disadvantages. Some are specifically designed for stability of temperature while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some are a combination, such as the E61. This is a very popular choice for baristas as it provides a variety of benefits in one package.

As you can see in the above image the group head is made up of several notches to put your portafilter, then twist it with your hands to lock it in. There is also a gasket made of rubber which is located inside the notches to help create an airtight seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is crucial to ensure an accurate extraction.

In addition to allowing you easily place your portafilter in, the group head is also responsible to ensure that the temperature remains even. It does this by circulating hot water through the brew pan and around the portafilter, making sure that it's always at the correct temperature to extract. It is important to note that even a small difference can make the difference between a good and a excellent espresso.

The Pump

Contrary to manual piston machines which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to provide the nine atmospheric bars of pressure necessary to extract espresso. The pressure is created by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pumped through the ground coffee in the group head.

Pumps tend to be less expensive and last for longer than piston-driven machines. However, both types of machines may degrade because of excessive use and insufficient cleaning. Pumps are also more complicated mechanically, which can raise the cost of even simple models.

Some espresso machines make use of steam pressure instead of a pump to make espresso. This can lead to over-extraction as the boiler that makes steam also warms the water to boil. Additionally these machines are often required to rebuild their pressure between cups, which takes time and energy.

Many espresso machines employ either a rotary or vibration pump, with a vibrating model using a rotating disc that generates the pressure, and rotating models that push hot water through the grounds at high speed. Both machines can make excellent espresso, however rotary machines are more quiet, durable and less likely to fail.

The Boiler

The boiler is the element that heats water to the ideal temperature for extraction. The steam that is created gets to the portafilter which holds the espresso grounds. It is then funneled into the cup. The steam generates enough pressure to push the grounds of the coffee through. This creates a foam on top of the espresso. This is one of the hallmarks of a great espresso.

There are three types of espresso machines, each with different pumps and brew temperature. There are various ways that the brew can be controlled and the size of the cup that the machine can produce.

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

The most commonly used espresso machine is a semiautomatic model with an electric pump. These are what people imagine when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans yourself The pump, however, regulates the water flow and pressure. This is an excellent compromise between human touch and the mechanized quality.

The Filter

Espresso machines usually have filters that separate the coffee grounds from the hot water. The filter is also an important component of the temperature control system because it stops the machine from overheating.

A filter can also help with flavor because it allows for the beans to flower for a longer period of time. This allows the beans to release their flavor and improves extraction.

It is important to remember that even the best bean to cup espresso machine filter can produce a bad cup of coffee. The quality of the beans as well as the extraction, are still very important.

This is where the magic happens, and it's what makes cheap espresso machine taste great. The grouphead, often called the brew head, is where the portafilter (the container you place the coffee grounds into) sits when you're making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam. Steam is then pushed through the grounds at high pressure. They are less expensive and easier to maintain than pumps-driven models. However, they are limited in their capacity to create the perfect brewing conditions since they are only operating at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.

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