How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and amazing filter technology to make the coffee we love. But how exactly does it work?

Espresso is made by forcing hot water under high pressure through finely-ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.

The Head of the Group

The group head is the portafilter you place in the espresso maker when making it. It disperses water in the portafilter, and then regulates the pressure of the extraction. There are a variety of types of group head, each with their particular advantages and drawbacks. Some are designed to provide the stability of temperature while some are specifically designed to handle pre-infusion. Others are built to control the lever. Some have a combination of features, such as the E61 one, which is the most popular choice among baristas for its ability to offer multiple perks in one package.

As you can see from the image above the head of the group is equipped with several notches. It is possible to place your portafilter into these notches and twist the head to secure it. A gasket made of rubber is placed inside the notches, which helps create a seal as you insert your portafilter. The notches on the head allow for a precise placement of the portafilter, which is essential for an efficient extraction.

The group head is not just able to allow the portafilter to be inserted easily but also maintains a constant temperature. This is accomplished by cycling hot water around the portafilter and through the brew-basket, making sure the temperature is always right for extraction. This is vital, because even a small difference in temperature can make the difference between a excellent and great espresso.

The Pump

Contrary to manual piston machines which rely on a lever that pressurize water, the rotary espresso machines use motorized pumps to supply the nine atmospheric bars of pressure needed for espresso extraction. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are typically less expensive and last for longer than piston-driven machines. However, both kinds of machines can deteriorate because of excessive use and poor cleaning. They also increase the complexity of mechanical systems which can result in costly prices for even the most basic models.

Some espresso machines employ steam pressure instead of a pump to brew espresso. The disadvantage of this is that the boiler that produces steam also increases the temperature of water until it reaches boiling which could lead to over-extraction. These machines also have to continuously rebuild their pressure between cups. This takes energy and time.

Many espresso machines make use of either a rotary or vibration pump, with a vibrating model that uses a vibrating disc to generate the pressure, and the rotary model pushing hot water through the grounds under high speed. Both machines can make excellent espresso however rotary machines tend to be more quiet, durable and less likely to break down.

The Boiler

The boiler is what heats the water to the ideal temperature to extract. The resulting steam is then transferred to the portafilter which holds the ground espresso coffee, and is then pumped down into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This results in a layer crema that is then poured over. This is one of the hallmarks of a good espresso.

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

The first espresso machines were steam-types. They employed only one boiler to make both steam and brew however the pressure they were able to generate was low - only two bars of atmospheric pressure at the most. The coffee tasted bitter and burned. The modern espresso machine was designed by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most commonly used espresso machine is a semiautomatic that has an electric pump. This is what people envision when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans by yourself The pump, however, regulates the water flow and pressure. This is a great combination of human control and mechanised consistency.

The Filter

Typically, espresso machines use filters to separate the grounds of coffee as they move through the hot water. The filter is also a vital component of the machine's temp control, since it helps to prevent overheating.

Filters also aid in flavor because it espresso machine sale allows for an extended flowering time. This lets the beans release their flavors, and allows for better extraction.

However, it is important to remember that even a great filter can produce a bad cup of coffee as the quality of the beans and extraction is still essential.

This is where the magic happens, it's the thing that makes espresso taste good. The grouphead, sometimes called the brew head, is where the portafilter (the device you put the coffee ground into) is located when you're making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through grounds of coffee under high pressure. These machines are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability for creating the ideal brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, espresso machines powered by a compressed air pump have become increasingly popular. They use an air compressor to force hot water through grounds and are more portable than electric steam-driven machines.