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How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and incredible filter technology to produce the perfect cup of coffee. What exactly does it work?

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

The Head of the Group

As the name implies, the group head is the place you place your portafilter while making espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure that results from the extraction. There are numerous kinds of group heads each with distinct advantages and disadvantages. Some are designed for stability of temperature while others are designed to handle pre-infusion. Others are made to control the lever. There are even some that have a combination of features, like the E61 that is to be the most popular among baristas due to its ability to offer multiple benefits in a single package.

As you can see from the above photo the group head is equipped with several notches. You place your portafilter into these notches and twist the head to lock it. A rubber gasket is located in the notches to create a seal while you insert your portafilter. The notches allow for precise placement of the portafilter. This is crucial for an efficient extraction.

The group head not only allows the portafilter to be inserted easily however, it also keeps the same temperature. This is done by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is always at the right level to extract the coffee. It is important to remember that even a small deviation can make the difference between a good and a great 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 needed to extract espresso. The pressure is created by drawing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the ground coffee inside the group head.

Pumps tend to be cheaper than piston-driven models, and they tend to last longer, however both types of machines can become damaged due to excessive use and poor cleaning. Pumps are also more complicated mechanically, which can raise the cost of even simple models.

Certain espresso machines can eliminate the pump completely and instead use steam pressure to brew espresso. The disadvantage of this is that the boiler that produces steam also raises the temperature of the water until it reaches boiling which can cause excessive extraction. The machines also need to continually rebuild their pressure between cups. This takes energy and time.

A large majority of espresso coffee machine machines employ an rotary or a vibration pump. A vibration model uses a vibrating disk to generate pressure, while a rotating model pushes hot water through the ground at a fast speed. Both types of machines are capable of producing excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the part which heats the water to the ideal temperature to extract. The resulting steam reaches the portafilter which holds the ground best espresso maker coffee and is then pumped down into the cup. The steam generates enough pressure to push the grounds of the coffee through. This creates a crema on the top of the espresso. This is a hallmark of a great espresso.

There are three kinds of espresso makers. They differ in the type of pump they employ and the degree of heat that the brew is. There are different ways to control the strength of the brew and the size of the cup that can be produced by the machine.

The first espresso machines were steam-based. The first espresso machines were steam-type machines. The coffee tasted bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most commonly used espresso maker is a semiautomatic machine with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic espresso machine, you need to grind the beans and then tamp them yourself but the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanized accuracy.

The Filter

Typically, espresso machines employ filters that separate 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.

It also improves flavor, as a filter allows for a more prolonged bloom phase. This allows beans to release their flavors and provides an opportunity for a better extraction.

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

It's in this area that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead, often called the brew head, is where the portafilter (the thing you put the ground coffee into) is placed when making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to create steam. The steam then pushes hot water through grounds of the coffee under pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited in their ability to create 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, espresso machines espresso machines powered by compressed air-pump have become increasingly popular. They use an air-compressor to force hot water into the ground and are more mobile than electric steam-driven espresso machines.