How Does Machine Espresso Work?

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

To make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However, the pressure is the main difference.

The Group Head

As the name implies, the group head is where you put your portafilter in when brewing espresso. It disperses the water into the portafilter and controls the pressure of the extraction. There are many different kinds of group heads, each with their distinct advantages and disadvantages. Some are focused on temperature stability, others on pre-infusion capabilities, and still others are designed to control the lever. Some come with a combination of both, like the E61. This is a very popular choice for baristas since it provides multiple advantages in one package.

As you can see from the picture above the head of the group is fitted with several notches. You can place your portafilter into these notches and twist the head to lock it. There is also a gasket made of rubber that resides inside the notches and helps create an airtight seal after inserting your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is vital for an efficient extraction.

In addition to allowing you easily connect your portafilter, the group head is also responsible for maintaining an even temperature. This is achieved by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is at the right level to extract the coffee. It is important to realize that even a slight deviation can make the difference between a decent and a great espresso.

The Pump

Motorized pumps in espresso machines that rotate provide the nine atmospheric bar pressure required for espresso extraction. This is different from manual piston machines that use a lever. The pressure builds up by removing tap water from a reservoir, and pumping it through a heat exchanger prior to being pumped through the ground coffee inside the group head.

Pumps are typically less expensive than piston-driven models, and they tend to last longer. However, Electric Espresso maker both types of machine can get damaged through overuse and lack of cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simple models.

Certain espresso machines utilize steam pressure instead of a pump to make espresso. This can cause over-extraction because the boiler that produces steam also heats the water until it comes to a boil. These machines also have to constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines utilize the rotary or vibration pump, with a vibration model using a vibrating disc to create the pressure and a rotary model pushing hot water through the grounds under high speed. Both machines can produce excellent espresso, however rotary machines are more quiet, durable and less likely to break down.

The Boiler

The boiler is used to heat the water to a temperature that is ideal to extract. The steam produced reaches the portafilter, which holds the espresso grounds. It is then funneled into the cup. The steam creates pressure that pushes through the coffee grounds. This creates a foam on top of the espresso. This is one of the main characteristics of a great espresso.

There are three types of espresso makers, which differ in the type of pump they employ and how hot the coffee is. There are various ways in which the brew could be controlled and the size of the cup the machine can produce.

The first espresso machines were steam-types. They had a single boiler to make both brew and steam, but the pressure they could create was minimal – two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most popular espresso machine is a semiautomatic one with an electric pump. This is what people envision when they think of an espresso maker. With a semi-automatic machine you need to grind the beans and then tamp them by hand, but the pump is able to regulate the flow of water and pressure. This is a perfect solution that combines human control with mechanised reliability.

The Filter

Typically, espresso machines employ a filter to separate out the grounds of coffee as they move through the hot water. The filter is also an essential component of the machine’s temp control, since it helps to prevent overheating.

It also helps with flavor, since a filter allows for a longer bloom time. This helps the beans release their nuances and gives an opportunity to improve extraction.

It is important to keep in mind that even the best filter can result in a bad cup of coffee. The quality of the beans and the extraction process remain vital.

It’s in this area that the magic occurs. This is what makes espresso taste so good. The grouphead (also known as the brewhead) is where you place the portafilter, the thingy used to place the coffee grounds into, when making espresso.

Steam-driven espresso machines make use of hot water that is heated in an airtight container to make steam. The steam then pushes hot water through coffee grounds under high pressure. These kinds of machines tend to be cheaper and easier to maintain than pump-driven models. They are however limited for creating 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, travel espresso maker machines driven by a compressed air pump have become increasingly popular. They utilize an air compressor to force hot water through grounds and are significantly more portable than steam-driven electric Espresso Maker machines.