How Does Machine Espresso Work?

The machine espresso is made using precision pressure, and a filtering technology that is amazing to make the coffee you enjoy. How exactly does it work?

In order to make espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, but the difference is in the pressure.

The Head of the Group

As the name implies, the group head is the place you place your portafilter while brewing espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are many different kinds of group head, each with their unique advantages and drawbacks. Some are specifically designed for stability of temperature while others are designed to handle pre-infusion. Others are built to control the lever. There are some that contain a variety of features, such as the E61, which is the standard choice for many baristas due to its ability to offer multiple perks in a single package.

As you can see in the photo above the head of the group is fitted with a variety of notches. It is possible to place your portafilter in these notches, then turn the head around to secure it. There is also a rubber gasket in the notches and helps create an airtight seal after inserting your portafilter into the machine. The notches permit an exact placement of the portafilter. This is crucial for an even extraction.

The group head does not just allow you to insert your portafilter easily however it also keeps the temperature at a constant level. This is achieved by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is always at the right level to extract the coffee. It is crucial to keep in mind that even a slight variation can mean the difference between a good and great espresso.

The Pump

The motorized pumps used in espresso machines that rotate provide the nine atmospheric bars of pressure required to extract espresso. This differs from manual piston machines that use levers. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally less expensive than piston-driven machines, and they tend to last longer, however both types of machines can get damaged through overuse and lack of cleaning. They also make mechanically complex that can lead to an expensive price for even the simplest models.

Some espresso machines do away with the pump completely and instead employ steam pressure to create espresso. This can result in over-extraction because the boiler that makes steam also causes the water to boil. In addition these machines are often required to restore their pressure between cups, which takes time and energy.

Many espresso machines make use of the rotary or vibration pump. A vibration model utilizes the vibrating disk to create pressure, whereas the rotating model read more pushes hot water through the ground at a rapid speed. Both machines can make great espresso but rotary machines are more quiet, durable and less likely to break.

The Boiler

The boiler is the one that will heat the water to the ideal temperature for extraction. The resultant steam then reaches the portafilter, which contains the ground espresso coffee and is then pumped down into the cup. During this process, steam creates pressure that pushes through the coffee grounds. This results in a layer of crema on top. This is a sign of a good espresso.

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

The first espresso machines were steam-types. They used only one boiler to make both steam and brew but the pressure they could produce was not very high - two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. This is why the Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most well-known espresso maker is a semiautomatic machine with an electric pump. This is what people envision when they think of an espresso maker. With a semi-automatic machine you have to grind the beans and tamp them by hand. The pump is able to regulate the flow of water and pressure. This is an excellent compromise between human control and mechanized reliability.

The Filter

Espresso machines usually use a filter that separates the grounds of the coffee from the hot water. The filter is also a vital component of the temperature control system as it keeps the machine from overheating.

A filter also helps with flavor since it allows for the beans to flower for a longer period of time. This helps the beans release their flavor and gives an opportunity for a better extraction.

It is important to keep in mind that even the finest filter can result in a bad cup of coffee. The quality of the beans and the extraction, are still very important.

This is where the magic happens, it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you put the portafilter - the thingy that you use to put the coffee grounds into, when making espresso.

In the steam-driven espresso machine hot water is heated in an airtight tank to create steam, which then pushes the hot water through the grounds at a high pressure. They are less expensive and easier to maintain than pumps-driven models. They are however limited in their ability to create the perfect conditions for brewing, as they operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

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