How Does Machine Espresso Work?

Machine espresso uses precision pressure and amazing filter technology to make the perfect cup of coffee. How exactly does it work?

Espresso is made by pushing hot water under pressure through finely-ground coffee. The process is similar to that of making drip coffee. However it is the pressure that makes the main difference.

The Head of the Group

As the name suggests the group head is where you put your portafilter in when making espresso maker barista. It is responsible for dispersing the water into the portafilter before controlling the pressure of the extraction. There are several different types of group head, each with their own advantages and disadvantages. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Others are built to control the lever. There are even some that contain a variety of features, like the E61, which is the standard choice for many baristas because of its ability to provide multiple benefits in a single package.

As you can see from the picture above the group head is fitted with several notches. The portafilter is placed into these notches and turn the head around to secure it. A rubber gasket is located within the notches to create a seal when you insert your portafilter. The notches on the head allow for an exact location of the portafilter which is necessary to ensure a consistent extraction.

The group head not only lets you to insert your portafilter easily however, it also keeps the same temperature. It does this by circulating hot water through the brew pan and around the portafilter, ensuring that it is always at the right temperature for extraction. It is crucial to keep in mind that even a few degree difference can make the difference between a great and a excellent espresso.

The Pump

In contrast to manual piston machines which rely on a lever that pressurize water, Best Small Espresso Machine rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure needed to extract espresso. The pressure builds by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being pushed through the ground coffee in the group head.

Pumps are typically less expensive than piston-driven machines, and tend to last longer, although both types of machines can be damaged by excessive use and inadequate cleaning. Pumps are also more complex mechanically, and can add to the cost of even the simplest models.

Certain espresso machines eliminate the pump completely and use steam pressure to brew espresso. This could lead to over-extraction since the boiler that produces steam also causes the water to boil. In addition, these machines frequently have to rebuild their pressure between cups, which takes time and energy.

Many espresso machines make use of an rotary or a vibration pump. A vibration model uses an oscillating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at high speed. Both models can make excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the part that heats water to an optimal temperature for extraction. The steam that is produced will eventually reach the portafilter, which holds the espresso grounds. It is then poured into the cup. The steam generates enough pressure to push the grounds of coffee through. This results in a whipped-up top of the espresso. This is one of the main characteristics of a good espresso.

There are three types of espresso machines, each with a different type of pump and brew temperature. There are also different ways that the brew can be controlled, as well as the size of the cup the machine is capable of making.

The first espresso machines were steam-types. They used only one boiler to make both brew and Coffeee steam, however, the pressure they could generate was low - only two bars of atmospheric pressure maximum. This led to the coffee tasting bitter and burnt. This is why Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanised consistency.

The Filter

Typically, espresso machines employ a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a crucial component of the temperature control system, because it stops the machine from overheating.

It also helps with flavor as a filter lets you enjoy a longer bloom phase. This lets the beans release their nuances, and allows for better extraction.

It is important to remember that even the best filter can produce a bad cup of coffee. The quality of the beans, and the extraction, are still very important.

It's here that the magic occurs. This is what makes espresso taste so good. The grouphead, often referred to as the brew head, is where the portafilter (the device you put the ground coffee in) is placed when you're making espresso.

Steam-driven espresso machines make use of hot water heated in an airtight container to produce steam. The steam then pushes hot water into the grounds of coffee at high pressure. These types of machines are typically less expensive and easier to maintain than pump-driven models. They are however limited to create the perfect brewing conditions as they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to force hot water into the ground and are much more mobile than electric steam-driven espresso machines.