How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to create the delicious coffee we enjoy. What exactly is it that makes it work?

In order to make espresso home machine hot water is pushed under pressure through finely ground coffee and espresso maker. The process is similar to that of making drip coffee. However, it is the pressure that makes the main difference.

The Group Head

As the name suggests the group head is the place you insert your portafilter when making 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 heads, each with their own advantages and disadvantages. Some are designed for stability in temperature, while others are designed to handle pre-infusion. Others are built to control the lever. There are even some that have a combination of features, such as the E61, which is the standard choice for many baristas due to its capacity to provide multiple benefits in one package.

As you can see in the photo above the group head is made up of many notches in which you can place your portafilter before twisting it by hand to secure it. There is also a gasket made of rubber that resides inside the notches and helps to create the seal when you insert your portafilter into the machine. The notches on the head permit an exact position of the portafilter which is essential to ensure a consistent extraction.

In addition to allowing you to easily insert your portafilter, the group head is also responsible for maintaining an even temperature. It does this by circulating hot water through the brew basket and around the portafilter, making sure that it is always at the right temperature to extract. It is important to realize that even a tiny difference can make the difference between a great and a great mini Espresso machine.

The Pump

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

Pumps are typically less expensive than piston-driven models, and they tend to last longer, although both types of machines could degrade with overuse and insufficient cleaning. They also make mechanically complex that can lead to costly prices for even the most basic models.

Certain espresso machines remove the pump completely and make use of steam pressure to make espresso. This can result in over-extraction because the boiler that produces steam also causes the water to boil. The machines also need to constantly rebuild their pressure in between cups. This takes energy and time.

Many espresso machines employ either a rotary or vibration pump, with a vibration model that uses a vibrating disc to create pressure and an rotary model that pushes hot water through the grounds at high speed. Both machines can produce excellent pro espresso machine but rotary machines are more quiet, durable and less likely to fail.

The Boiler

The boiler is what heats the water to a temperature that is ideal to extract. The resultant steam then reaches the portafilter containing the ground espresso coffee and gets funnelled down into the cup. During this process the steam causes enough pressure to push the grounds of the coffee through. This results in a layer of crema that is then poured over. This is one of the main characteristics of a good espresso.

There are three distinct types of espresso machines, each having different types of pumps and the temperature of the brew. There are various ways that the brew can be controlled, as well as the size of the cup that the machine can make.

The earliest espresso machines were steam types. They had only one boiler to make both steam and brew however the pressure they were able to produce was not very high - two bars of atmospheric pressure at most. This led to the coffee tasting bitter and burnt. 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. When people think of espresso machines, they picture these machines. Semi-automatic machines require you to grind and tamp your beans yourself, but the pump regulates the flow of water and pressure. This is a perfect solution that combines human control with mechanized accuracy.

The Filter

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

A filter can also help with flavor, as it permits the beans to flower for a longer period of time. This helps the beans let their nuances out and provides an opportunity for better extraction.

It is important to keep in mind that even the best filter can make a bad cup of coffee. The quality of the beans and the extraction, remain crucial.

This is where the magic happens. It's what makes an espresso really taste good. The grouphead, also referred to as the brew head, is the place where the portafilter (the container you place the coffee ground into) is placed when making espresso.

In a steam-driven espresso machine, hot water is heated in an airtight container to produce steam, which then pushes the hot water through the grounds under high pressure. These machines are less expensive and easier for the owner to maintain than pumps-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 ideal 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 the hot water through the grounds and are significantly more portable than electric steam-driven machines.