How Does Machine Espresso Work?

Machine espresso uses precision pressure and incredible filter technology to produce the delicious coffee we enjoy. What exactly does it work?

Espresso is created by forcing hot water under high pressure through finely-ground coffee. The process is similar to making drip coffee. However, the pressure is the major difference.

The Group Head

The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing the water into the portafilter before controlling the pressure that results from the extraction. There are many different kinds of group heads each with its distinct advantages and disadvantages. Some focus on temperature stability, some on pre-infusion capabilities, and still others are designed to control the lever. Some include a combination like the E61. This is a preferred choice for baristas due to the fact that it has multiple advantages in a single package.

As you can see in the image 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 gasket made of rubber that resides inside the notches to help create a seal when you insert your portafilter into the machine. The notches permit precise placement of your portafilter. This is essential for an efficient extraction.

In addition to allowing you to easily place your portafilter in, the group head is also responsible to maintain an even temperature. This is achieved by cycling hot water around the portafilter, and through the brew basin, ensuring that the temperature is at the right level for extraction. It is important to note that even a tiny variation can mean the difference between a good and a excellent espresso.

The Pump

The motorized pumps that are used in rotary espresso machines supply the nine atmospheric bar pressure needed to extract espresso. This is different from manually operated piston machines that employ levers. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are typically cheaper and last longer than piston-driven machines. However, both types of machines can degrade due to overuse and poor cleaning. They also add mechanical complexity which can result in an expensive price for even the simplest models.

Certain espresso machines utilize steam pressure instead of a pump in order to brew espresso. This can lead to over-extraction as the boiler that makes steam also causes the water to boil. These machines also have to constantly rebuild their pressure in between cups. This requires energy and time.

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

The Boiler

The boiler is what makes the water warm to the perfect temperature to extract. The resultant steam then reaches the portafilter containing the ground espresso coffee, and is then pumped down into the cup. During this process the steam is able to create enough pressure to push the grounds of the coffee through. This creates a foam on top of the espresso. This is one of the main characteristics of a good espresso.

There are three types of espresso makers, which differ in the type of pump they employ and the degree of heat that the espresso is. There are also different ways in which the brew can be controlled, as well as the size of the cup that the machine can produce.

The earliest espresso machines were steam types. They utilized one boiler to make both steam and brew but the pressure they could generate was low - only two bars of atmospheric pressure maximum. This led to the coffee tasting burnt and bitter. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most common espresso machine is a semiautomatic with an electric pump. When people think of espresso coffee machine machines, they imagine these machines. If you have a semi-automatic machine you have to grind the beans and tamp them by hand. However, the pump controls the flow of water and pressure. This is an excellent compromise between human touch and the mechanized consistency.

The Filter

professional espresso maker machines typically have filters that separate the grounds of coffee from hot water. The filter is also an essential component of the machine's temp control, as it helps prevent overheating.

A filter also improves flavor, as it permits a longer flowering period. This helps the beans release their flavors and provides the chance for better extraction.

It is important to keep in mind that even the best espresso machine under 500 (sneak a peek here) filter can result in a bad cup of coffee. The quality of the beans, as well as the extraction, are still crucial.

This is where the magic happens, it's what makes espresso machine with milk frother taste great. The grouphead (also called the brewhead) is where you place the portafilter - the thingy used to place the coffee machines espresso grounds in, when making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to create steam. The steam then moves hot water through the grounds of coffee at high pressure. They 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 conditions for brewing since 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 been gaining popularity. They utilize an air compressor to push hot water into the grounds and are more portable than steam-driven electric machines.