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How Does Machine Espresso Work?

Machine espresso employs precise pressure and amazing filter technology to make the coffee we love. What exactly is it?

Espresso is created by forcing hot water at high pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.

The Group Head

The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure of the resulting extraction. There are many different kinds of group head each with its unique advantages and drawbacks. Some focus on temperature stability, others on pre-infusion options, and others are designed to control the lever. There are some that include a mix of features, like the E61 one, which is to be the most popular among baristas because of its ability to offer multiple perks in a single package.

As you can see from the photo above, the group head has a number of notches. You place your portafilter inside these notches, and then twist the head to lock it. There is also a gasket of rubber that is a part of the notches and helps to create an airtight seal after inserting your portafilter into the machine. The notches allow for precise placement of the portafilter. This is vital for an accurate extraction.

The group head not only allows you to insert your portafilter easily however it also keeps the same temperature. It does this by circulating hot water through the brew basket and around the portafilter to ensure that it is always at the right temperature to extract. This is vital, because just a few degrees could make the difference between a excellent and great espresso.

The Pump

Unlike manual piston machines, which rely on a lever to pressurize water, rotating espresso coffee machine home machines rely upon motorized pumps that provide the nine atmospheric bars of pressure that are required for espresso extraction. The pressure is built by pumping water through a heat exchanger and then through the ground coffee.

Pumps are typically more affordable and last longer than piston-driven machines. However, both kinds of machines may degrade because of frequent use and insufficient cleaning. They also increase the complexity of mechanical systems and can lead to an expensive price for even the most basic models.

Some espresso machines can eliminate the pump completely and instead use steam pressure to brew espresso. The disadvantage of this is that the same boiler that produces steam also raises the temperature of water until it reaches boiling which could lead to excessive extraction. The machines must also constantly rebuild their pressure between cups. This requires energy and time.

A majority of espresso machines utilize a rotary or vibration pump. A vibration model utilizes the vibrating disk to create pressure, while the circular model pushes hot liquid through the ground at a rapid speed. Both types of machine can make excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is used to heat the water to the right temperature for extraction. The steam that is produced reaches the portafilter, which holds the espresso grounds. It is then poured into the cup. The steam creates pressure and pushes through the coffee for espresso machine grounds. This results in a crema on the top of the espresso. This is one of the main characteristics of a good espresso.

There are three distinct types of espresso machines, each having different pumps and the temperature of the brew. There are a variety of ways to control the brew and the size of cup that can be made by the machine.

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

The most well-known home espresso machine maker is a semi-automatic one with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic espresso machine, you need to grind the beans and tamp them by hand. The pump provides regulated water flow and pressure. This is a great compromise between the human touch and mechanized quality.

The Filter

Espresso machines usually use filters that separate the grounds of the coffee from hot water. The filter is also a vital element of the temperature control system as it prevents the machine from overheating.

It also aids in flavor, as it allows for a longer bloom phase. This allows the beans to release their flavors and provides an opportunity for a better extraction.

However, it is important to remember that even a top filter could result in a bad cup of coffee, since the quality of the beans and extraction are essential.

It's here that the magic takes place. This is the reason why espresso tastes so good. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you use to put the coffee grounds into, while making espresso.

Steam-driven espresso machine coffee machines make use of hot water heated in an airtight vessel to create steam. The steam then pushes hot water through coffee grounds under high pressure. They are less expensive 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 powered by a compressed air pump have become increasingly popular. They make use of an air compressor to force hot water through the ground and are much more mobile than steam-driven electric espresso machines.