How Does Machine Espresso Work?

Machine espresso (Meshbookmarks.com) uses precision pressure and mind-blowing filter technology to create the coffee we love. What exactly does it work?

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

The Head of the Group

The name implies the group head is where you place your portafilter when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the resulting extraction. There are several different types of group head, each with their distinct advantages and disadvantages. Some are specifically designed for stability in temperature, while others are built to handle pre-infusion. Some are designed to control the lever. Some are a combination, like the E61. This is a favorite among baristas as it provides a variety of benefits in a single package.

As you can see in the image above the group head is made up of several notches to place your portafilter before twisting it manually to lock it in. A gasket made of rubber is placed in the notches to create a seal while you insert your portafilter. The notches on the head permit a precise positioning of the portafilter which is necessary for an even extraction.

Aside from allowing you to easily connect your portafilter, the group head is responsible for maintaining an even temperature. It does this by circulating hot water through the brew basket, and around the portafilter, ensuring that it's always at the correct temperature to extract. It is important to realize that even a slight differences can make the distinction between a good and a excellent espresso.

The Pump

The motorized pumps used in rotary espresso machines provide the nine atmospheric bar pressure needed to extract espresso. This is different from manual piston machines that rely on levers. The pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger prior being pushed through the ground coffee inside the group head.

Pumps are generally less expensive and last for longer than piston-driven machines. However, both types of machines may degrade due to overuse and poor cleaning. Pumps are also more complicated mechanically, which can increase the price of even the simplest models.

Some small espresso machine machines can eliminate the pump completely and instead make use of steam pressure to make home espresso machine. This can result in over-extraction because the boiler that produces steam also warms the water to boil. They also have to constantly rebuild their pressure in between cups. This takes energy and time.

Many espresso machines employ an rotary or vibrating pump, with a vibrating model using a vibrating disc to create pressure and an rotary model that pushes hot water through the grounds under high speed. Both models are capable of producing excellent top espresso machines, however rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler heats the water to the right temperature for extraction. The steam that is created will eventually reach the portafilter, which is the container that holds the espresso coffee grounds. The steam is then channeled into the cup. During this process the steam causes enough pressure to push the grounds of the coffee through. This results in a layer crema that is then poured over. This is one of the main characteristics of a great espresso.

There are three distinct types of espresso machines, each having different pumps and brew temperature. There are various ways that the brew may be controlled and the dimensions of the cup the maker can create.

The first espresso machines were steam-type. They utilized one boiler to create both brew and steam, however, the pressure they could create was minimal - two bars of atmospheric pressure maximum. The coffee tasted bitter and burnt. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso maker is a semi-automatic one that has an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans on your own, but the pump regulates the flow of water and pressure. This is a perfect combination of human control and mechanized consistency.

The Filter

Typically, espresso machines employ filters to separate the grounds of coffee when they pass through the hot water. The filter is also a vital element of the machine's temperature control, since it helps to prevent overheating.

It also aids in flavor as a filter allows for a longer bloom phase. This helps the beans release their nuances and gives an opportunity for a better extraction.

It is important to remember that even the most efficient filter can result in a bad cup of coffee. The quality of the beans and the extraction process, remain crucial.

It's in this area that the magic takes place. This is what makes espresso taste so good. The grouphead (also called the brewhead) is where you place the portafilter, the device which you put the grounds of your coffee into when making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then moves hot water through the grounds of coffee at high pressure. These types of machines are usually less expensive and easier to maintain than pump-driven models. They are however limited to create the ideal conditions for brewing since they only operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

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