How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to make the coffee we love. What 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 difference is in the pressure.

The Head of the Group

The group head is the portafilter is inserted when you are making espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are many different types of group heads each with distinct advantages and drawbacks. Some focus on temperature stability, whereas others on pre-infusion capabilities, and still others are designed to control the lever. There are even some that have a combination of features, such as the E61 that is the standard choice for many baristas because of its ability to provide multiple benefits in one package.

As you can see in the above image, the group head has several notches to place your portafilter and twist it by hand to secure it. There is also a gasket made from rubber that is a part of the notches and helps create an airtight seal when you insert your portafilter into the machine. The notches on the head permit a precise placement of the portafilter, which is necessary to ensure a consistent extraction.

Aside from allowing you to easily place your portafilter in, the group head is also responsible to ensure that the temperature remains even. It does this by circulating hot water through the brew container and around the portafilter to ensure that it's always at the correct temperature to extract. This is vital, because just a few degrees could be the difference between a good and excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, Rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure that are required to extract espresso. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger prior being pumped through the ground coffee inside the group head.

Pumps tend to be cheaper than piston-driven machines and tend to last longer, but both types of machines may get damaged through overuse and lack of cleaning. They also create mechanical complexity that can lead to the cost of even the simplest models.

Some espresso machines can eliminate the pump entirely and make use of steam pressure to make espresso. The downside is that the same boiler that produces steam also increases the temperature of the water until it reaches boiling which can cause over-extraction. The machines also need to continuously rebuild their pressure between cups. This requires energy and time.

A majority of espresso machines utilize either a vibration or rotary pump. A vibration model employs the vibrating disk to create pressure, while a rotary model pushes hot water through the ground at high speed. Both types of machine can make excellent espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler heats the water to the right temperature to extract. The resulting steam reaches the portafilter that contains the ground espresso coffee and is then pumped down into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This results in a whipped-up top of the espresso. This is one of the main characteristics of a good espresso.

There are three types of espresso makers. They differ in the type of pump they employ and the degree of heat that the brew is. There are different ways to control the amount of brew, as well as the size of the cup that can be produced by the machine.

The earliest espresso machines were steam type. They utilized one boiler to create steam and brew, however the pressure they were able to produce was not very high - two bars of atmospheric pressure maximum. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most common decent espresso machine maker is a semi-automatic one with an electric pump. This is what people envision when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized accuracy.

The Filter

Espresso machines usually use a filter that separates the grounds of the coffee from the hot water. The filter is also an important part of the temperature control system, as it prevents the machine from overheating.

Filters also aid in flavor because it allows for a longer flowering period. This helps the beans to release their flavors and provides the chance for better extraction.

However, it is important to remember that even a good filter could result in a bad cup of coffee as the quality of the beans and extraction is still vital.

It's in this area that the magic takes place. This is what makes espresso taste so delicious. The grouphead (also called the brewhead) is where you place the portafilter, which is the thingy that you put the coffee grounds into, while making espresso.

Steam-driven buy espresso machines machines use hot water that is heated in an airtight container to create steam. The steam then pushes hot water through coffee grounds under high pressure. These kinds of machines are typically less expensive and easier to maintain than pump-driven models. They are however limited 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, retro espresso machine machines driven by a compressed air pump have become increasingly popular. They use an air compressor to force the hot water through the grounds and are more portable than electric steam-driven machines.