How Does Machine Espresso Work?

Machine espresso uses precision pressure and amazing filter technology to make the perfect cup of coffee. What exactly is it that makes it work?

Espresso is created by forcing hot water under high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However, it is the pressure that makes the main difference.

The Group Head

The group head is the portafilter that you insert when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the extraction. There are many different kinds of group heads each with its distinct advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion options, and others are designed to control the lever. Some are a combination, like the E61. This is a very popular choice for baristas because it offers multiple benefits in a single package.

As you can see from the picture above the group head has a number of notches. It is possible to place your portafilter in these notches, then turn the head around to secure it. A gasket made of rubber is placed in the notches to create a seal when you insert your portafilter. The notches on the head permit a precise placement of the portafilter, which is vital to ensure a consistent extraction.

Apart from allowing you easily place your portafilter in, the group head is also responsible to ensure that the temperature remains even. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring the temperature is always right for extraction. This is important because even a small difference in temperature can make the difference between a good and great espresso.

The Pump

In contrast to piston machines that are manually operated, which rely on a lever to pressurize water, rotating espresso machines home machines rely upon motorized pumps to provide the nine atmospheric bars of pressure necessary for espresso extraction. The pressure is created by pumping water through a heat-exchanger and then through the best ground coffee for espresso machine coffee.

Pumps are typically less expensive than piston-driven machines and tend to last longer. However, both types of machines can become damaged due to excessive use and poor cleaning. They also create mechanical complexity, which can result in a high price tag on even the most basic models.

Some espresso machines do away with the pump entirely and make use of steam pressure to make espresso. The downside is that the boiler that produces steam also increases the temperature of water to the point of boiling and can result in over-extraction. In addition these machines are often required to rebuild their pressure between cups, which requires time and energy.

A majority of espresso machines use the rotary or vibration pump, which is a vibration model that uses a vibrating disc to create pressure and a rotary model pushing hot water through the grounds at high speed. Both models are capable of producing excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is what makes the water warm to the perfect temperature to extract. The resultant steam then reaches the portafilter which holds the ground espresso coffee and is then pumped into the cup. In this process, the steam causes pressure to push through the coffee grounds. This results in a layer crema that is then poured over. This is a hallmark of a great espresso.

There are three kinds of espresso makers, which differ in the kind of pump they use and how hot the brew is. There are different ways to control the brew and the size of cup that can be made by the machine.

The first espresso machines were steam-types. They utilized only one boiler to make both brew and steam, but the pressure they could produce was very low - just two bars of atmospheric pressure, espresso machines home at most. The coffee tasted bitter and burned. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most commonly used espresso machine is a semiautomatic with an electric pump. These are what people imagine when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp your beans yourself, but the pump regulates the water flow and pressure. This is a fantastic compromise between human control and mechanised accuracy.

The Filter

Espresso machines typically use a filter that separates the grounds of the coffee from the hot water. The filter is also a vital part of the machine's temperature control, as it prevents overheating.

A filter also improves flavor since it allows for a longer flowering phase. This lets the beans let their nuances out, and also allows for better extraction.

It is important to keep in mind that even the finest filter can produce a bad cup of coffee. The quality of the beans, as well as the extraction, remain vital.

This is where the magic happens. It's what makes espresso taste great. The grouphead (also called the brewhead) is where you place the portafilter - the thingy that you use to put the coffee grounds into, when making espresso.

Steam-driven home espresso machine machines make use of hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through grounds of coffee at high pressure. These machines are cheaper and easier to maintain than pumps-driven models. However, they are limited in their ability to create the ideal brewing conditions, as they only operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bars.

In recent years, compressed air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to force hot water through the ground, and are more mobile than electric steam-driven espresso machines.