9 . What Your Parents Teach You About Machine Espresso

How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to make the perfect cup of coffee. What exactly is it?

Espresso is created by forcing hot water at high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However the pressure is the primary difference.

The Group Head

As the name implies, the group head is the place you put your portafilter in when making espresso. It disperses water in the portafilter, and then regulates the pressure during the extraction. There are several different types of group head, each with their own advantages and disadvantages. Some are specifically designed for stability of temperature while others are designed to handle pre-infusion. Others are made to control the lever. There are also some that have a combination of features, such as the E61 that is the classic choice among many baristas for its ability to offer multiple perks in one package.

As you can see in the above photo the group head comes with many notches in which you can place your portafilter before twisting it with your hands to lock it in. A gasket of rubber is situated inside the notches to help make a seal when you insert your portafilter. The notches on the head permit an exact positioning of the portafilter which is vital to ensure an efficient extraction.

The group head does not just allow you to place your portafilter easily but also maintains an even temperature. This is done by cycling hot water around the portafilter and through the brew basin, ensuring the temperature is always right for extraction. This is important because even a small difference in temperature can make the difference between a good and great espresso.

The Pump

In contrast to manual piston machines which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to deliver the nine atmospheric bars of pressure needed bean to cup espresso machine extract espresso. 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 are generally less expensive than piston-driven machines, and tend to last longer. However, both types of machines could get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, which can increase the cost of even the simpler models.

Certain espresso machines can eliminate the pump completely and utilize steam pressure to make espresso. The disadvantage of this is that the boiler that produces steam also raises the temperature of the water to boiling and can result in excessive extraction. In addition these machines are often required to rebuild their pressure between cups, which requires time and energy.

A majority of espresso machines utilize either a vibration or rotary pump. A vibration model uses a rotating disk to generate pressure, while a circular model pushes hot liquid through the ground at high speed. Both machines can produce excellent espresso, however rotary machines are more quiet, durable and less likely to break.

The Boiler

The boiler heats the water to the perfect temperature to extract. The steam that is created will eventually reach the portafilter, which contains the espresso coffee grounds. It is then poured into the cup. The steam creates enough pressure to push the grounds of the coffee through. This creates a foam on top of the espresso. This is one of the hallmarks of a great espresso.

There are three types of espresso machines, each having distinct pumps and brew temperature. There are many ways to control the brew and the size of the cup that can be made by the machine.

The earliest espresso machines were steam-based. They had one boiler to make steam and brew, but the pressure they could produce was very low - just two bars of atmospheric pressure at most. The coffee espresso machine tasted bitter and burnt. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most commonly used espresso maker is a semiautomatic machine that has an electric pump. This is what people envision when they imagine an espresso machines home machine. If you have a semi-automatic machine you grind the beans and then tamp them by hand. However, the pump provides regulated water flow and pressure. This is a great compromise between the human touch and mechanized 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 vital component of the machine's temperature control, since it helps to prevent overheating.

A filter can also help with flavor because it allows for a longer flowering period. This allows the beans to release their nuances, and also allows for better extraction.

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

It's here that the magic occurs. This is what makes espresso taste so good. The grouphead, also called the brewhead, is where the portafilter (the device you put the ground coffee in) is placed when making espresso.

Steam-driven espresso machines use hot water that is heated in an airtight container to make steam. The steam then pushes hot water into the grounds of the coffee under pressure. These machines are less expensive and are easier for the user to maintain than pumps-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 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 hot water through the grounds and are significantly more portable than steam-driven electric machines.