How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to make the coffee we love. But how exactly does it work?

In order to make espresso, hot water is forced 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 put in when making espresso. It disperses water into the portafilter, and regulates the pressure of the extraction. There are various kinds of group heads, each with their unique advantages and disadvantages. Some are specifically designed for stability of temperature while others are built to handle pre-infusion. Others are made to control the lever. There are even some that come with a range of features, such as the E61, which is the standard choice for many baristas due to its ability to provide multiple benefits in one package.

As you can see in the photo above, the group head has several notches to put your portafilter, then twist it manually to secure it. A gasket of rubber is situated inside the notches, which helps create a seal as you insert your portafilter. The notches permit an exact placement of the portafilter. This is crucial for a consistent extraction.

Apart from allowing you easily place your portafilter in, the group head is responsible to maintain an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket, making sure the temperature is always right to extract the coffee. It is important to note that even a tiny deviation can make the difference between a decent espresso machine and a excellent espresso.

The Pump

In contrast to piston machines that are manually operated, which use a lever to pressurize water, rotary espresso machines rely on motorized pumps that provide the nine atmospheric bars of pressure required for espresso extraction. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally less expensive and last for longer than piston-driven machines. However, both types of machines can degrade because of frequent use and insufficient cleaning. Pumps are also more complex mechanically, which can raise the price of even the most basic models.

Some espresso machines make use of steam pressure instead of a pump to make espresso. This can result in over-extraction because the boiler that makes steam also causes the water to boil. Additionally, these machines frequently have to restore their pressure between cups, which takes time and energy.

A majority of espresso machines use either a rotary or vibration pump, which has a vibration model using a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds at high speed. Both machines can produce excellent espresso but rotary machines are more quiet, durable and less likely to break.

The Boiler

The boiler is the one that heats the water to the perfect temperature to extract. The steam that is created is then directed to the portafilter, which is a container for barista espresso coffee machine grounds. It is then pumped into the cup. During this process, the steam causes pressure to push through the grounds of the coffee. This creates a crema on the top of the espresso. This is one of the main characteristics of a good espresso.

There are three different types of espresso machines, each having different types of pumps and the temperature of the brew. There are also different ways that the brew may be controlled as well as the dimensions of the cup the machine is capable of making.

The first espresso machines were steam-types. They utilized one boiler to create steam and brew, however, the pressure they could produce was not very high - two bars of atmospheric pressure, espressomachines at most. This resulted in the coffee tasting bitter and burnt. This is why the Milanese producers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most commonly used espresso machine is a semiautomatic model with an electric pump. These are the images people have when they imagine an espresso machine. Semi-automatic espresso machine machines require you to grind and tamp your beans yourself while the pump controls the water flow and pressure. This is a great compromise between the human touch and mechanized quality.

The Filter

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

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

However it is crucial to keep in mind that even a great filter could result in a bad cup of coffee, because the quality espresso machine of the beans and extraction is still vital.

This is where the magic happens. It's what makes espresso taste great. The grouphead, sometimes called the brew head, is the place where the portafilter (the thingy you put the coffee grounds into) is located when you're making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then pushes hot water through grounds of coffee at high pressure. These kinds of machines are usually cheaper and easier to maintain than pump-driven models. However, they are limited in their ability to provide the perfect brewing conditions since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bar.

In recent years, compressed-air-pump-driven espresso machines have become more popular. They utilize an air compressor to push hot water across the ground and are much more mobile than steam-driven electric espresso machines.