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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. What exactly does it work?

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

The Head of the Group

The name implies, the group head is where you place your portafilter while brewing espresso coffee machines for sale. It is responsible for dispersing water into the portafilter before controlling the pressure that results from the extraction. There are many different types of group heads each with its own advantages and disadvantages. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Some are designed to control the lever. Some have a combination, like the E61. This is a popular choice among baristas since it provides multiple benefits in a single package.

As you can see in the photo above, the group head is fitted with several notches. It is possible to place your portafilter in these notches and then turn the head around to secure it. There is also a rubber gasket in the notches to help create a seal when you insert your portafilter into the machine. The notches on the head permit an exact position of the portafilter which is vital for an efficient extraction.

The group head is not just able to allow you to insert your portafilter easily however it also keeps an even temperature. This is done by cycling hot water around the portafilter and through the brew-basket, making sure that the temperature is constant to extract the coffee. This is crucial, since just a few degrees could be the difference between a excellent and great espresso.

The Pump

In contrast to manual piston machines which rely on a lever that pressurize water, rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure that are required to extract espresso. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are typically less expensive than piston-driven machines, and tend to last longer, however both types of machines may be damaged by excessive use and inadequate cleaning. They also increase the complexity of mechanical systems, which can result in the cost of even the simplest models.

Certain espresso machines remove the pump completely and make use of steam pressure to make espresso. This can lead to over-extraction as the boiler that produces steam also heats the water to boil. The machines must also continuously rebuild their pressure between cups. This requires energy and time.

Many espresso machines make use of the rotary or vibration pump, which is a vibration model using a vibrating disc to create the pressure and rotating models that push hot water through the grounds at high speed. Both types of machine can produce an excellent espresso, however the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler will heat the water to the ideal temperature for extraction. The steam that is created gets to the portafilter which is the container that holds the espresso coffee grounds. It is then poured into the cup. During this process the steam generates enough pressure to push the coffee grounds through. This produces a layer of crema that is then poured over. This is the hallmark of a great espresso.

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

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

The most well-known espresso maker is a semi-automatic machine that has an electric pump. When people think of espresso machines, they imagine these machines. Semi-automatic machines require you to grind and tamp the beans yourself The pump, however, regulates the flow of water and pressure. This is a great compromise between the human touch and the mechanised quality.

The Filter

Typically, espresso machines have filters to separate the coffee grounds as they pass through the hot water. The filter is also an important element of the temperature control system as it keeps the machine from overheating.

It also helps with flavor, as a filter lets you enjoy a longer bloom time. This helps the beans release their flavor and gives an opportunity for a better extraction.

It is important to keep in mind that even the most efficient filter can make a bad cup of coffee. The quality of the beans as well as the extraction, are still crucial.

It's here that the magic happens. This is what makes espresso taste so good. The grouphead, sometimes called the brew head, is where the portafilter (the container you place the ground coffee in) is placed when you're making best budget espresso machine.

Steam-driven espresso coffee machine home machines use hot water that is heated inside an airtight container to make steam. The steam then moves hot water through the grounds of the coffee under pressure. These kinds of machines are usually less expensive and simpler to maintain than pumps-driven models. However, they are limited in their ability to provide the ideal conditions for brewing as they only operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.

In recent years, compressed-air-pump-driven espresso and filter coffee machine machines have become more popular. They use an air compressor to push hot water through grounds, and are far more portable than electric steam-driven machines.