How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and amazing filter technology to make the coffee we love. What exactly does it work?

Espresso is made by pushing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee however the main difference lies in the pressure.

The Group Head

The name implies, the group head is where you put your portafilter in when making espresso. It is responsible for Machine Espresso dispersing the water into the portafilter and controlling the pressure of the extraction. There are many different kinds of group head each with its distinct advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. There are some that include a mix of features, like the E61 one, which is the classic choice among many baristas due to its ability to provide multiple benefits in one package.

As you can see in the photo above the group head is equipped with several notches. It is possible to place your portafilter inside these notches, and then turn the head around to secure it. There is also a rubber gasket which is located inside the notches to help create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact placement of the portafilter, which is vital for a consistent extraction.

The group head is not just able to allow you to put in your portafilter easily however it also keeps the temperature at a constant level. It does this by cycling hot water through the brew pan and around the portafilter, ensuring that it is always at the correct temperature to extract. It is important to remember that even a slight variation can mean the difference between a decent and a great espresso.

The Pump

Motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure required to extract espresso. This is different from manual piston machines that use levers. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger prior to being pushed through the ground coffee inside the group head.

Pumps tend to be more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate because of frequent use and poor cleaning. Pumps are also more complex mechanically, which could increase the cost of even simplest models.

Some espresso machines do away with the pump entirely and use steam pressure to brew espresso. This can result in over-extraction because the boiler that makes steam also heats the water to boil. The machines also need to continuously rebuild their pressure between cups. This takes energy and time.

Many espresso machines make use of a rotary or vibration pump. A vibration model makes use of a rotating disk to generate pressure, whereas the Rotary model pushes hot coffee through the ground at a fast speed. Both machines produce great espresso maker for home but rotary machines are quieter, more durable and less likely to break down.

The Boiler

The boiler will heat the water to the perfect temperature for extraction. The steam that is created gets to the portafilter which is the container that holds the espresso coffee grounds. It is then funneled into the cup. During this process, steam creates pressure to push through the coffee grounds. This produces a layer of crema that is then poured over. This is the hallmark of a great espresso.

There are three types of espresso machines, each having distinct pumps and brew temperature. There are different ways that the brew may be controlled, as well as the size of the cup that the machine is capable of making.

The first espresso machines were steam-type. They used only one boiler to make both steam and brew however the pressure they were able to produce was very low - just two bars of atmospheric pressure at most. The coffee tasted bitter and burnt. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most common espresso machine is a semiautomatic that has an electric pump. When people think of espresso machines, they picture these machines. If you have a semi-automatic machine you need to grind the beans and then tamp them by hand, but the pump provides regulated water flow and pressure. This is a fantastic solution that combines human control with mechanized consistency.

The Filter

Espresso machines typically use filters that separate the grounds of the coffee from the hot water. The filter is also an essential component of the machine's temp control, since it stops overheating.

A filter also improves flavor because it allows for an extended flowering time. This allows the beans to release their flavor and allows for better extraction.

It is important to keep in mind that even the most efficient filter can make a bad cup of coffee. The quality of the beans, as well as the extraction, are still crucial.

It's in this area that the magic takes place. This is what makes espresso taste so delicious. The grouphead (also called the brewhead) is where you put the portafilter - the thingy that you use to put the coffee grounds in, when making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight tank to create steam. Steam then pushes the hot water through the grounds at high pressure. These kinds of machines tend to be cheaper and easier to maintain than pumps-driven models. They are however limited in their ability for creating the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, compressed air pump-driven espresso machines have become more popular. They use an air compressor to force hot water through grounds, and are far more portable than steam-driven electric machines.