How Does Machine Espresso Work?

The machine espresso uses precision pressure, and filtering technology that is amazing to make the coffee you enjoy. What exactly does it work?

Espresso is produced by pushing hot water under high pressure through finely-ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure.

The Group Head

The group head is the portafilter that you place in the espresso maker when making it. It is responsible for dispersing the water into the portafilter before controlling the pressure that results from the extraction. There are various kinds of group heads, each with their particular advantages and disadvantages. Some focus on temperature stability, while others on pre-infusion capabilities, and still others are designed to control the lever. There are some that include a mix of features, like the E61 that is the most popular choice among baristas due to its capacity to offer multiple perks in a single package.

As you can see from the picture above the group head is fitted with several notches. It is possible to place your portafilter in these notches and then turn the head around to secure it. There is also a gasket made of rubber that resides inside the notches and helps create the seal when you insert your portafilter into the machine. The notches on the head allow for an exact position of the portafilter which is essential for an efficient extraction.

In addition to allowing you to easily insert your portafilter, the group head is responsible to ensure that the temperature remains even. It does this by circulating hot water through the brew basket and around the portafilter, ensuring that it is always at the right temperature for extraction. This is crucial, since even a small difference in temperature can make the difference between good and excellent espresso.

The Pump

Contrary to manual piston machines which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure needed for espresso extraction. The pressure builds by removing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.

Pumps tend to be less expensive than piston-driven machines, and they tend to last longer, however both types of machines may become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, which can increase the cost of even simple models.

Some espresso machines remove the pump completely and utilize steam pressure to make espresso. The disadvantage of this is that the same boiler that produces steam also raises the temperature of water to boiling which could lead to over-extraction. These machines also have to continuously rebuild their pressure between cups. This requires energy and time.

A majority of espresso machines utilize an rotary or a vibration pump. A vibration model makes use of a rotating disk to generate pressure, while a rotary model pushes hot water through the ground at a rapid speed. Both machines can make excellent espresso however rotary machines tend to be more quiet, durable and less likely to fail.

The Boiler

The boiler is the element which heats the water to the ideal temperature to extract. The steam produced gets to the portafilter which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process, the steam causes pressure to push through the coffee grounds. This creates a foam on the top of the espresso. This is the hallmark of a great espresso.

There are three types of espresso makers. They differ in the kind of pump they use and the degree of heat that the espresso machine with frother is. There are a variety of ways to control the strength of the brew and the size of the cup that can be produced by the machine.

The first espresso machines were steam types. They had one boiler to make both brew and steam, however, the pressure they could produce was very low - just two bars of atmospheric pressure, at most. This resulted in the coffee tasting bitter and burnt. The modern espresso machine was developed by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso maker is a semiautomatic machine with an electric pump. These are the things people think of when they think of an espresso maker. If you have a semi-automatic machine you have to grind the beans and espresso maker tamp them by hand, but the pump regulates the flow of water and pressure. This is a great combination of human control and mechanized reliability.

The Filter

Espresso machines usually use filters that separate the coffee grounds from the hot water. The filter is also a crucial part of the temperature control system as it keeps the machine from overheating.

A filter also improves flavor, as it permits the beans to flower for a longer period of time. This lets the beans let their nuances out, and improves extraction.

It is important to remember that even the most efficient filter can result in a bad cup of coffee. The quality of the beans and the extraction, remain vital.

It's here that the magic happens. This is the reason why espresso tastes so good. The grouphead, sometimes called the brewhead, is where the portafilter (the container you place the coffee grounds into) sits when you're making espresso.

Steam-driven espresso machines make use of hot water heated in an airtight container to make steam. The steam then pushes hot water into the grounds of coffee at high pressure. These machines are less expensive and 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, espresso machines powered by compressed air-pump have become increasingly popular. They make use of an air compressor to push hot water through the ground and are more mobile than electric steam-driven espresso machines.