How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to make the delicious coffee we enjoy. How exactly does it work?

To make an espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure.

The Head of the Group

The group head is the portafilter you place in the espresso maker when making it. It is responsible for dispersing water into the portafilter and controlling the pressure that results from the extraction. There are numerous kinds of group heads each with their own advantages and disadvantages. Some focus on temperature stability, while others on pre-infusion capabilities, while others are designed to control the lever. Some are a combination, like the E61. This is a popular choice among baristas since it provides multiple benefits in one package.

As you can see in the above image, the group head has numerous notches that you can place your portafilter and twist it by hand to lock it in. There is also a gasket of rubber that is a part of the notches and helps create a seal when you insert your portafilter into the machine. The notches on the head allow for a precise position of the portafilter which is essential to ensure an even extraction.

In addition to allowing you to easily place your portafilter in, the group head is also responsible for maintaining an even temperature. This is done by cycling hot water around the portafilter, and through the brew-basket, making sure the temperature is always right for extraction. It is important to note that even a few degree differences can make the distinction between a good and a great espresso.

The Pump

The motorized pumps used in rotary espresso machines espresso machines supply the nine atmospheric bar pressure that is required to extract espresso. This differs from manual piston machines which use a lever. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are typically less expensive and last longer than piston-driven machines. However, both types of machines can degrade due to excessive use and poor cleaning. They also make mechanically complex and can lead to an expensive price for even the simplest models.

Some espresso machines make use of steam pressure instead of a pump in order to brew espresso. This can result in over-extraction because the boiler that produces steam also causes the water to boil. In addition these machines are often required to rebuild their pressure between cups, which takes time and energy.

Many espresso machines employ a vibration or rotary pump, with a vibrating model using a rotating disc to generate the pressure and rotating models that push hot water through the grounds at high speed. Both machines can produce excellent espresso, however rotary machines are more quiet, durable and less likely to fail.

The Boiler

The boiler makes the water warm to the right temperature for extraction. The steam that is created is then directed to the portafilter, which contains the espresso coffee grounds. It is then pumped into the cup. During this process the steam is able to create enough pressure to push the grounds of coffee through. This results in a whipped-up the top of the espresso. This is one of the hallmarks of a great espresso.

There are three kinds of espresso makers, which differ in the type of pump they use and the degree of heat that the espresso is. There are a variety of ways to control the brew as well as the size of cup that can be made by the machine.

The first espresso machines were steam-types. The first espresso machines were steam-type machines. This led to the coffee tasting burnt and bitter. This is why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most commonly used espresso maker is a semi-automatic machine with an electric pump. These are the images people have when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans yourself however the pump controls the flow of water and pressure. This is a perfect compromise between human control and mechanised accuracy.

The Filter

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

It also improves flavor, since a filter allows for a longer bloom time. This lets the beans release their nuances, and improves extraction.

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

This is where the magic happens, it's the thing that makes an espresso really taste good. The grouphead, also referred to as the brew head, is where the portafilter (the device you put the coffee grounds into) is located when you're making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to create steam. The steam then pushes hot water through grounds of coffee under high pressure. These types of machines are typically cheaper and easier to maintain than pump-driven models. They are however limited to create the ideal conditions for brewing as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, espresso machines powered by compressed air-pump have become increasingly popular. They use an air compressor to push hot water into the grounds and are significantly more portable than electric steam-driven machines.