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How Does Machine Espresso Work?

Machine espresso uses precision pressure and incredible filter technology to produce the perfect cup of coffee. What exactly is it?

In order to make barista espresso machine hot water is pushed under 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 disperses the water into the portafilter, and then regulates the pressure during the extraction. There are many different kinds of group head, each with their own advantages and drawbacks. Some are designed for stability of temperature while others are designed to handle pre-infusion. Some are designed to control the lever. Some have a combination, such as the E61. This is a very popular choice for baristas because it offers multiple advantages in a single package.

As you can see in the above image the group head is made up of many notches in which you can place your portafilter and twist it with your hands to lock it in. A gasket made of rubber is placed inside the notches, which helps create a seal when you insert your portafilter. The notches on the head permit an exact position of the portafilter which is vital for an even extraction.

The group head not only allows you to insert your portafilter easily but also maintains a constant temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is at the right level to extract the coffee. It is crucial to keep in mind that even a few degree variation can mean the difference between a great and a excellent espresso.

The Pump

The motorized pumps in rotary espresso machines supply the nine atmospheric bars of pressure required to extract espresso. This is different from manual piston machines that rely on levers. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be less expensive than piston-driven machines, and tend to last longer, although both types of machines can become damaged due to excessive use and poor 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 use steam pressure instead of a pump to brew espresso. This can cause over-extraction because the boiler that produces steam also heats the water to boil. These machines also have to constantly rebuild their pressure in between cups. This takes energy and time.

Many espresso machines use an rotary or a vibration pump. A vibration model employs an oscillating disk to create pressure, whereas a rotating model pushes hot water through the ground at a fast speed. Both machines can produce excellent espresso but rotary machines are quieter, more durable and less likely to break down.

The Boiler

The boiler is the component that heats water to the optimal temperature to extract. The resulting steam is then transferred to the portafilter containing ground espresso beans and is then funneled down into the cup. The steam creates pressure to push through the grounds of the coffee. This creates a crema on 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 various ways in which the brew could be controlled and the size of the cup the machine can make.

The first espresso machines were steam-based. They had one boiler to make both steam and brew however, the pressure they could produce was very low - just two bars of atmospheric pressure at the most. The coffee tasted bitter and burned. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso maker is a semiautomatic machine with an electric pump. When people think of espresso machines, they think of these machines. With a semi-automatic espresso machine, you have to grind the beans and tamp them by hand, but the pump regulates the flow of water and pressure. This is a fantastic compromise between human control and mechanised reliability.

The Filter

Espresso machines typically have a filter that separates the grounds of the coffee from the hot water. The filter is also an essential component of the temperature control system, because it stops the machine from overheating.

It also improves flavor, as a filter can allow for a longer bloom phase. This allows the beans to let their nuances out, and allows for better extraction.

However it is crucial to keep in mind that even a high-quality filter can make a terrible cup of coffee, since the quality of the beans and extraction is vital.

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 thingy that you put the coffee grounds into, while making espresso.

Steam-driven espresso machines make use of hot water that is heated in an airtight vessel to create steam. The steam then pushes hot water through the grounds of the coffee under pressure. These kinds of machines are generally less expensive and simpler to maintain than pump-driven models. They are however limited to create the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent times, espresso machines powered by compressed air-pump have become increasingly popular. They utilize an air compressor to force hot water through the best ground coffee for espresso machine and are more mobile than electric steam-driven espresso machines.