How Does Machine Espresso Work?

Machine espresso employs precise pressure and incredible filter technology to produce the coffee we love. How exactly does it work?

Espresso is produced by pushing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee, but the difference is in the pressure.

The Group Head

The group head is the portafilter you insert when brewing professional espresso machine for home. It distributes water into the portafilter, and regulates the pressure during the extraction. There are many different types of group heads each with distinct advantages and disadvantages. Some are designed for temperature stability while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some come with a combination of both, like 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 image above the group head is equipped with several notches. You can place your portafilter in these notches, then twist the head to secure it. There is also a gasket of rubber that resides inside the notches and helps to create an airtight seal when you insert your portafilter into the machine. The notches on the head allow for a precise positioning of the portafilter which is necessary to ensure an efficient extraction.

Apart from allowing you easily connect your portafilter, the group head is responsible to ensure that the temperature remains even. It does this by cycling hot water through the brew basket and around the portafilter, ensuring that it is always at the right temperature to extract. This is crucial, since even a few degrees can make the difference between a good and great espresso.

The Pump

Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure required to extract espresso. This differs from manual piston machines which use levers. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be cheaper and last longer than piston-driven machines. However, both kinds of machines can deteriorate because of excessive use and insufficient cleaning. Pumps are also more complex mechanically, which can increase the cost of even simplest models.

Certain espresso machines utilize steam pressure instead of a pump for brewing espresso. The drawback of this is that the boiler that produces steam also increases the temperature of water to the point of boiling which can cause excessive extraction. In addition the machines often have to rebuild their pressure between cups, which requires time and energy.

Many espresso machines employ a vibration or rotary pump, which has a vibration model that uses a vibrating disc to create pressure and a rotary model pushing hot water through the grounds under high speed. Both machines produce great espresso however rotary machines tend to be quieter, more durable and less likely to break.

The Boiler

The boiler is what makes the water warm to the right temperature to extract. The resultant steam then reaches the portafilter containing the ground espresso coffee, and is then funneled down into the cup. The steam creates enough pressure to push the grounds of the coffee through. This results in a layer crema that is then poured over. This is one of the main characteristics of a great espresso.

There are three types of espresso makers, and they differ in the type of pump they use and how hot the brew is. There are various ways in which the brew can be controlled and the size of the cup the machine can make.

The first espresso machines were steam-type. They employed one boiler to create steam and brew, but the pressure they could produce was not very high - two bars of atmospheric pressure at most. The coffee tasted bitter and burned. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso machine is a semiautomatic that has an electric pump. This is what people envision when they think of an espresso machine. With a semi-automatic espresso machine, you have to grind the beans and then tamp them by hand. The pump regulates the flow of water and pressure. This is a great combination of human control and mechanized reliability.

The Filter

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

It also helps with flavor, as it can allow for a longer bloom phase. This helps the beans release their flavor and gives an opportunity for better extraction.

It is important to keep in mind that even the best filter could result in a poor cup of coffee. The quality of the beans, and the extraction, remain crucial.

It's here that the magic happens. This is what makes espresso taste so delicious. The grouphead (also known as the brewhead) is where you put the portafilter - the thingy that you use to put the grounds of coffee into while making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through grounds of the coffee under pressure. These types of machines tend to be cheaper and easier to maintain than pump-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 powered by a compressed air compressor have become increasingly popular. They use an air compressor to push hot water across the ground and are much more mobile than steam-driven electric espresso machines.