How Does Machine Espresso Work?

Machine espresso utilizes precise pressure and mind-blowing filter technology to create the coffee we love. But how 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 major difference.

The Group Head

The group head is the portafilter you place in the espresso maker when making it. It distributes water into the portafilter, and then regulates the pressure of extraction. There are various kinds of group heads, each with their distinct advantages and drawbacks. Some are specifically designed for stability of temperature while others are designed to handle pre-infusion. Others are built to control the lever. Some have a combination, such as the E61. This is a favorite among baristas since it provides multiple advantages in one package.

As you can see from the above photo 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 positioned inside the notches, which helps create a seal while you insert your portafilter. The notches allow for precise placement of your portafilter. This is crucial for an even extraction.

The group head not only allows the portafilter to be inserted easily but also maintains a constant temperature. It does this by cycling hot water through the brew basket, and around the portafilter, making sure that it's always at the right temperature to extract. It is important to realize that even a slight deviation can make the difference between a good and a excellent espresso.

The Pump

In contrast to manual piston machines that use a lever to pressurize water, the rotary best small espresso machine machines use motorized pumps to provide the nine atmospheric bars of pressure needed for espresso extraction. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger before it is shot through the ground coffee in the group head.

Pumps are typically less expensive and last for longer than piston-driven machines. However, both types of machines can deteriorate due to excessive use and inadequate cleaning. They also create mechanical complexity which can result in costly prices for even the simplest models.

Some espresso machines employ steam pressure instead of a pump to brew espresso. This can cause over-extraction because the boiler that produces steam also warms the water to boil. Additionally these machines typically have to rebuild their pressure between cups, which takes time and energy.

A majority of espresso machines use a vibration or rotary pump, with a vibrating model using a vibrating disc to generate the pressure and a rotary model pushing hot water through the grounds under high speed. Both machines can make great espresso however rotary machines tend to be more stable, quieter and less likely to break down.

The Boiler

The boiler is the element that heats water to an ideal temperature for extraction. The steam created will eventually reach the portafilter, which contains the espresso coffee grounds. It is then poured into the cup. The steam is able to create enough pressure to push the grounds of coffee through. This creates a layer crema on top. This is a hallmark of a good espresso.

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

The first 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 the most. This resulted in the coffee tasting bitter and burnt. This is the reason Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most commonly used espresso maker is a semi-automatic device 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 The pump, however, regulates the water flow and pressure. This is a perfect compromise between human control and mechanized reliability.

The Filter

Espresso machines usually use a filter that separates the grounds of the coffee from hot water. The filter is also a vital element of the temperature control system, because it stops the machine from overheating.

Filters also aid in flavor since it allows for the beans to flower for a longer period of time. This allows the beans to release their flavors, and also allows for better extraction.

However it is crucial to remember that even a high-quality filter could result in a bad cup of coffee, since the quality of the beans and extraction are essential.

This is where the magic happens, and it's what makes espresso taste great. The grouphead, often referred to as the brewhead, is where the portafilter (the device you put the ground coffee in) sits when you're making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to produce steam. The steam then pushes hot water through the coffee grounds under high pressure. These machines are less expensive and easier for the owner to maintain than pumps-driven models. They are however limited in their ability to create the ideal conditions for brewing 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 compressed air-pump have become increasingly popular. They use an air compressor to push hot water into the grounds and are much more portable than electric steam-driven machines.