How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to make the coffee we love. What exactly is it?

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

The Group Head

As the name suggests the group head is the place you place your portafilter when making espresso. 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 for stability of temperature while others are specifically designed to handle pre-infusion. Some are designed to control the lever. There are even some that have a combination of features, such as the E61, which is considered the classic choice among many baristas due to its capacity to offer multiple benefits in a single package.

As you can see in the image above the group head is made up of many notches in which you can put your portafilter, then twist it by hand to lock it in. There is also a gasket made of rubber that is a part of the notches and helps create a seal when you insert your portafilter into the machine. The notches allow for precise placement of the portafilter. This is vital for a consistent extraction.

Apart from allowing you effortlessly insert your portafilter the group head is responsible for maintaining a consistent temperature. This is done by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is always at the right level for extraction. This is important, as even a few degrees can mean the difference between good and great espresso.

The Pump

Motorized pumps in rotary espresso machines provide the nine atmospheric bar pressure needed to extract espresso. This differs from manual piston machines that use a lever. This pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger before being pushed through the ground coffee inside the group head.

Pumps tend to be less expensive and last for longer than piston-driven machines. However, both types of machines can deteriorate due to excessive use and insufficient cleaning. They also add mechanical complexity that can lead to an expensive price for even the simplest models.

Certain espresso machines utilize steam pressure instead of a pump to brew espresso. The drawback is that the same boiler that produces steam also raises the temperature of the water to the point of boiling, which can lead to over-extraction. The machines espresso machines must also continually rebuild their pressure between cups. This takes energy and time.

Many espresso machines utilize a vibration or rotary pump, with a vibrating model that uses a vibrating disc that generates the pressure, and an rotary model that pushes hot water through the grounds at high speed. Both machines can make great espresso but rotary machines are more quiet, durable and less likely to break down.

The Boiler

The boiler is the element that heats water to the ideal temperature for extraction. The steam that is produced reaches the portafilter which holds the ground espresso coffee, and gets funnelled down into the cup. During this process, the steam causes pressure to push through the coffee grounds. This results in a whipped-up top of the espresso. This is one of the main characteristics of a great espresso.

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

The earliest espresso machines were steam-based. The first espresso machines were steam types. This led to the coffee tasting burnt and bitter. The modern espresso machine was created by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso maker is a semi-automatic one with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic espresso machine, you must grind the beans and then tamp them by hand. The pump controls the flow of water and pressure. This is an excellent compromise between human control and mechanised consistency.

The Filter

Espresso machines typically use a filter that separates the grounds of coffee from hot water. The filter is also a vital component of the machine's temperature control, as it helps prevent overheating.

It also enhances flavor as a filter allows for a longer bloom phase. This lets the beans release their flavor and allows for better extraction.

However it is crucial to keep in mind that even a good filter can produce a bad cup of coffee, as the quality of the beans and extraction is crucial.

This is where the magic happens, and it's what makes espresso taste great. The grouphead, often called the brewhead, 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 heated in an airtight vessel to create steam. The steam then pushes hot water into the grounds of coffee at high pressure. They are less expensive and are easier for the user to maintain than pumps-driven models. However, they are not as efficient in their ability to provide the ideal conditions for brewing since they operate at 1-1.5 bars of pressure. While the perfect shot requires 9-10 bars.

In recent years, compressed-air-pump-driven espresso machines have been gaining popularity. They utilize an air compressor to push hot water through grounds and are more portable than steam-driven electric machines.