How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and incredible filter technology to produce the coffee we love. But how exactly does it work?

In order to make espresso hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However, it is the pressure that makes the main difference.

The Group Head

The name implies, the group head is where you place your portafilter while brewing espresso. It disperses water into the portafilter, and then regulates the pressure during the extraction. There are various kinds of group heads each with its unique advantages and disadvantages. Some are designed to provide stability of temperature while others are built to handle pre-infusion. Others are built to control the lever. Some are a combination, like the E61. This is a very popular choice for baristas because it offers multiple advantages in one package.

As you can see in the above photo the group head is made up of several notches where you place your portafilter and twist it with your hands to lock it in. A gasket made of rubber is positioned inside the notches, which helps create a seal while you insert your portafilter. The notches on the head permit an exact location of the portafilter which is vital to ensure a consistent extraction.

The group head does not just allow you to place your portafilter easily, but it also maintains an even temperature. 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 for extraction. It is important to note that even a few degree variation can mean the difference between a great and a excellent espresso.

The Pump

Motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure needed to extract espresso. This is different from manual piston machines that rely on a lever. This pressure is generated by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally cheaper and last longer than piston-driven machines. However, both kinds of machines can degrade because of frequent use and inadequate cleaning. They also add mechanical complexity that can lead to the cost of even the most basic models.

Some espresso machines use steam pressure instead of a pump for brewing espresso. This could lead to over-extraction since the boiler that makes 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 the rotary or vibration pump. A vibration model employs the vibrating disk to create pressure, while a rotary model pushes hot water through the ground at a rapid speed. Both machines can produce excellent espresso, however rotary machines are more stable, quieter and less likely to fail.

The Boiler

The boiler makes the water warm to the perfect temperature for extraction. The steam that is produced reaches the portafilter containing the ground espresso and gets funnelled down into the cup. The steam creates enough pressure to push the coffee grounds through. This results in a whipped-up top of the espresso. This is one of the hallmarks of a good espresso.

There are three kinds of espresso makers, which differ in the kind of pump they use and how hot the coffee is. There are a variety of ways to control the strength of the brew and the size of the cup that can be made by the machine.

The first espresso machines were steam-type. They utilized one boiler to create both brew and steam, however the pressure they were able to create was minimal - two bars of atmospheric pressure maximum. This led to the coffee tasting burnt and bitter. The modern espresso machine was created by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they think of these machines. If you have a semi-automatic machine you need to grind the beans and tamp them yourself but the pump regulates the flow of water and pressure. This is an excellent compromise between human touch and the mechanized quality.

The Filter

Typically, espresso machines have filters to separate the grounds of coffee when they pass through the hot water. The filter is website also a crucial component of the temperature control system because it stops the machine from overheating.

Filters also aid in flavor since it allows for an extended flowering time. This allows beans to release their nuances and gives an opportunity to improve extraction.

However, it is important to keep in mind that even a top filter can produce a bad cup of coffee, because the quality of the beans and extraction are vital.

It's in this area that the magic takes place. This is the reason why espresso tastes so good. The grouphead (also called the brewhead) is where you place the portafilter - the thingy which you put the grounds of your coffee into when making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight container to create steam. This is then pushed through the grounds under high pressure. These machines are cheaper and easier to maintain than pumps-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 have become increasingly popular. They utilize an air compressor to push hot water through the grounds and are significantly more portable than electric steam-driven machines.