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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and amazing filter technology to make the delicious coffee we enjoy. How exactly does it work?

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

The Head of the Group

The group head is the portafilter you put in when making espresso. It disperses water in the portafilter, and then regulates the pressure of the extraction. There are many different kinds of group head each with its particular advantages and disadvantages. Some focus on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. Some come with a range of features, such as the E61, which is the standard choice for many baristas due to its ability to offer multiple benefits in one package.

As you can see in the image above, the group head has several notches to place your portafilter and then twist it with your hands to secure it. There is also a rubber gasket that is a part of the notches, which helps create a seal when you insert your portafilter into the machine. The notches on the head allow for a precise positioning of the portafilter which is crucial for a consistent extraction.

In addition to allowing you easily connect your portafilter, the group head is responsible for maintaining an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is constant for extraction. It is important to note that even a small variation can mean the difference between a great and a great espresso.

The Pump

The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure that is required for espresso extraction. This differs from manually operated piston machines that employ levers. The pressure builds up by removing tap water from a reservoir and pumping it through a heat exchanger prior to being pumped through the ground coffee inside the group head.

Pumps are typically cheaper and last longer than piston-driven machines. However, both kinds of machines may degrade due to excessive use and insufficient cleaning. Pumps are also more complicated mechanically, which could increase prices of even simpler models.

Certain espresso machines do away with the pump completely and make use of steam pressure to make espresso. This can result in over-extraction because the boiler that produces steam also heats the water to boil. These machines also have to constantly rebuild their pressure between cups. This requires energy and time.

Many espresso machines employ either a rotary or vibration pump, with a vibrating model using a vibrating disc to create pressure and an rotary model that pushes hot water through the grounds under high speed. Both models are capable of producing excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the part that heats water to the ideal temperature for extraction. The steam that is produced is then directed to the portafilter, which holds the espresso grounds. It is then funneled into the cup. During this process, the steam creates pressure that pushes through the grounds of the coffee. This results in a layer crema on top. This is one of the hallmarks of a good espresso.

There are three types of espresso makers, which differ in the type of pump they employ and the degree of heat that the coffee is. There are also different ways that the brew can be controlled and the size of the cup that the machine is capable of making.

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

The most popular espresso machine is a semiautomatic that has an electric pump. These are the images people have when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans by yourself while the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized consistency.

The Filter

Espresso machines usually have a filter that separates the grounds of the coffee from hot water. The filter is also an essential component of the machine's temp control, since it helps to prevent overheating.

It also improves flavor, as it can allow for a longer bloom phase. This lets the beans release their flavors, and allows for a better extraction.

It is important to remember that even the best bean to cup espresso machine filter can make a bad cup of coffee. The quality of the beans as well as the extraction, remain vital.

It's in this area that the magic happens. This is what makes espresso taste so delicious. The grouphead, sometimes referred to as the brew head, is the place where the portafilter (the thing you put the coffee grounds into) sits when you're making espresso.

Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water into the grounds of the coffee under pressure. These kinds of machines are usually less expensive and simpler to maintain than pump-driven models. However, they are limited in their ability to produce the ideal 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, espresso machines driven by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water through the ground, and are more mobile than electric steam-driven espresso machines.