Machine Espresso: The Ugly Reality About Machine Espresso

How Does Machine Espresso Work?

Machine espresso employs precise pressure and incredible filter technology to produce the perfect cup of coffee. 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 but the difference is in the pressure.

The Head of the Group

The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing water into the portafilter, and controlling the pressure that results from the extraction. There are various kinds of group heads each with its particular advantages and disadvantages. Some are focused on temperature stability, whereas others on pre-infusion features, and others are designed to control the lever. Some have a combination, such as the E61. This is a favorite among baristas as it provides a variety of advantages in one package.

As you can see in the photo above The group head features several notches to place your portafilter and then twist it by hand to secure it. A rubber gasket is located inside the notches to help create a seal as you insert your portafilter. The notches on the head permit a precise location of the portafilter which is vital to ensure an even extraction.

The group head is not just able to allow you to insert your portafilter easily however, it also keeps the temperature at a constant level. It does this by cycling hot water through the brew basket and around the portafilter to ensure that it's always at the correct temperature to extract. It is crucial to keep in mind that even a few degree difference can make the difference between a good and excellent espresso.

The Pump

Unlike manual piston machines, which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure required for espresso extraction. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be less expensive and last for longer than piston-driven machines. However, both types of machines can degrade due to overuse and poor cleaning. Pumps are also more complicated mechanically, which can increase prices of even most basic models.

Certain espresso machines can eliminate the pump entirely and use steam pressure to brew espresso. The drawback of this is that the boiler that produces steam also increases the temperature of water to boiling and can result in over-extraction. They also have to constantly rebuild their pressure between cups. This requires energy and time.

Many espresso machines utilize either a rotary or vibration pump, which is a vibration model using a vibrating disc to generate the pressure and a rotary model pushing hot water through the grounds under high speed. Both machines can make excellent espresso, but rotary machines are more quiet, durable and less likely machine espresso to break.

The Boiler

The boiler is the element which heats the water to the ideal temperature to extract. The steam produced will eventually reach the portafilter, which is the container that holds the espresso coffee grounds. It is then poured into the cup. During this process, the steam creates pressure to push through the coffee grounds. This results in a layer of crema that is then poured over. This is a sign of a good espresso.

There are three kinds of espresso makers. They differ in the type of pump they use and the degree of heat that the espresso is. There are also different ways in which the brew could be controlled, as well as the size of the cup that the maker can create.

The earliest espresso machines were steam-based. 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 bitter and burnt. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most commonly used espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they picture these machines. With a semi-automatic espresso machine, you need to grind the beans and tamp them by hand. However, the pump provides regulated water flow and pressure. This is a great combination of human control and mechanised consistency.

The Filter

Espresso machines usually use a filter that separates the coffee grounds from the hot water. The filter is also an essential element of the machine's temperature control, since it helps to prevent overheating.

Filters also aid in flavor because it allows for a longer flowering phase. This lets the beans release their flavor and improves extraction.

However it is crucial to keep in mind that even a great filter can make a terrible cup of coffee, since the quality of the beans and extraction are vital.

This is where the magic happens, and it's what makes an espresso really taste good. The grouphead, also referred to as the brew head, is the place where the portafilter (the thingy you put the ground coffee into) is placed when you're making espresso.

In a steam-driven espresso machine hot water is heated in an airtight tank to create steam. This is then pushed through the grounds at a high pressure. These types of machines tend to be cheaper and easier to maintain than pump-driven models. They are however limited in their ability 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, compressed air pump-driven espresso machines have become more popular. They use an air compressor to force the hot water through the grounds and are significantly more portable than steam-driven electric machines.