How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and incredible filter technology to produce the coffee we love. What exactly is it that makes it work?

Espresso is made by forcing hot water under pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.

The Group Head

The name implies the group head is where you insert your portafilter when making espresso. It distributes water into the portafilter, and regulates the pressure of extraction. There are many different types of group heads each with its own advantages and drawbacks. Some are specifically designed for temperature stability while others are specifically designed to handle pre-infusion. Some are designed to control the lever. Some come with a combination of both, such as the E61. This is a favorite among baristas as it provides a variety of benefits in one package.

As you can see in the image above the group head is made up of many notches in which you can put your portafilter, then twist it by hand to lock it in. There is also a gasket of rubber that resides inside the notches, which helps create an airtight seal after inserting your portafilter into the machine. The notches permit precise placement of the portafilter. This is essential for an accurate extraction.

In addition to allowing you to easily connect your portafilter, the group head is also responsible for maintaining a consistent temperature. This is done by cycling hot water around the portafilter, and through the brew-basket, ensuring the temperature is always right for extraction. It is crucial to keep in mind that even a small 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 needed for espresso extraction. This is different from manual piston machines that use a lever. This pressure is built up by pumping water through a heat-exchanger and then through the ground coffee.

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

Some espresso machines remove the pump completely and utilize steam pressure to make espresso. This can cause over-extraction because the boiler that produces steam also warms the water to boil. They also have to continuously rebuild their pressure between cups. This takes energy and time.

A majority of espresso machines use the rotary or vibration pump, which has a vibration model using a vibrating disc that generates the pressure and rotating models that push hot water through the grounds under high speed. Both types of machine can produce an excellent espresso, however the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is the one that will heat the water to the right temperature for extraction. The resulting steam reaches the portafilter which holds the ground espresso coffee, and is then funneled down into the cup. The steam generates enough pressure to push the grounds of coffee through. This results in a layer of crema on top. This is a sign of a great espresso.

There are three different types of professional espresso machine machines, each with different pumps and the temperature of the brew. There are a variety of ways in which the brew can be controlled and the size of the cup the machine can make.

The first espresso machines were steam-based. They employed one boiler to create both brew and steam, but the pressure they could create was minimal - two bars of atmospheric pressure maximum. This resulted in the coffee tasting burnt and bitter. This is the reason why Milanese makers Luigi Bezzerra and Desiderio Pavoni invented the modern espresso machine.

The most commonly used espresso maker for home maker is a semi-automatic device with an electric pump. This is what people envision when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself, but the pump regulates the flow of water and espressomachines pressure. This is a great compromise between the human touch and the mechanized consistency.

The Filter

Espresso machines typically have filters that separate the grounds of the coffee from hot water. The filter is also an essential part of the temperature control system, as it keeps the machine from overheating.

It also enhances flavor, as it lets you enjoy a longer bloom phase. This allows the beans to release their flavor and allows for a better extraction.

However it is crucial to keep in mind that even a great filter can make a terrible cup of coffee, because the quality of the beans and espressomachines extraction is still important.

It's in this area that the magic takes place. This is the reason why espresso tastes so delicious. The grouphead, sometimes called the brew head, is where the portafilter (the thingy you put the coffee ground into) is placed when you're making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water through coffee grounds under high pressure. These kinds of machines are generally less expensive and easier to maintain than pumps-driven models. However, they are not as efficient in their capacity to create the perfect brewing conditions since they are only operating 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 force hot water into the grounds, and are far more portable than steam-driven electric machines.