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How Does Machine Espresso Work?

The machine espresso uses precision pressure, and filtering system that is awe-inspiring to create the coffee you enjoy. How exactly does it work?

To make an espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee but the major difference is in the pressure.

The Head of the Group

The group head is the portafilter you place in the espresso maker when making it. It disperses the water into the portafilter, and regulates the pressure of extraction. There are several different types of group heads, each with their distinct advantages and disadvantages. Some are designed to provide stability in temperature, while others are built to handle pre-infusion. Others are made to control the lever. Some have a combination, like the E61. This is a popular choice among baristas because it offers multiple benefits in a single package.

As you can see in the image above, the group head has several notches to put your portafilter, then twist it with your hands to secure it. There is also a rubber gasket in the notches to help create an airtight seal after inserting your portafilter into the machine. The notches permit the precise placement of the portafilter. This is essential for an even extraction.

In addition to allowing you to easily place your portafilter in, the group head is also responsible for maintaining a consistent temperature. It does this by circulating hot water through the brew basket and around the portafilter, ensuring that it is always at the correct temperature to extract. It is important to note that even a tiny deviation can make the difference between a decent and a great espresso.

The Pump

In contrast to manual piston machines that use a lever to pressurize water, rotating espresso machines rely upon motorized pumps that provide the nine atmospheric bars of pressure necessary for espresso extraction. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger prior to being shot through the ground coffee inside the group head.

Pumps are generally more affordable and last longer than piston-driven machines. However, both types of machines can deteriorate due to overuse and insufficient cleaning. Pumps are also more complex mechanically, which could increase prices of even simple models.

Some espresso machines make use of steam pressure instead of a pump to make espresso. The disadvantage of this is that the boiler that produces steam also raises the temperature of the water to the point of boiling which can cause over-extraction. These machines also have to constantly rebuild their pressure in between cups. This requires energy and time.

A majority of espresso machines utilize a rotary or vibration pump. A vibration model makes use of the vibrating disk to create pressure, while a circular model pushes hot liquid through the best ground coffee for espresso machine at a high speed. Both machines produce great espresso, but rotary machines are quieter, more durable and less likely to break.

The Boiler

The boiler is what is used to heat the water to a temperature that is ideal to extract. The resulting steam reaches the portafilter which holds the ground espresso coffee, and is then funneled 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 great espresso.

There are three kinds of espresso makers, and they differ in the type of pump they use and the degree of heat that the coffee is. There are also different ways in which the brew can be controlled, as well as the size of the cup that the machine can produce.

The earliest espresso machines were steam type. They utilized only one boiler to make steam and brew, however the pressure they were able to create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. This is the reason Milanese makers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most commonly used espresso maker is a semi-automatic device with an electric espresso maker pump. These are what people imagine when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans on your own however the pump controls the flow of water and pressure. This is a great compromise between the human touch and the mechanised quality.

The Filter

Espresso machines usually use a filter that separates the grounds of the coffee from hot water. The filter is also a crucial part of the temperature control system as it keeps the machine from overheating.

A filter can also help with flavor as it allows for a longer flowering period. This helps the beans to release their flavor and gives an opportunity to improve extraction.

It is important to remember that even the finest filter can produce a bad cup of coffee. The quality of the beans, and the extraction process, are still crucial.

This is where the magic happens. It's what makes an espresso really taste good. The grouphead (also called the brewhead) is where you put the portafilter - the thingy used to place the coffee grounds into, when making espresso.

In a steam-driven espresso home machine machine hot water is heated in an airtight tank to create steam. This is then pushed through the grounds at a high pressure. These machines are less expensive and easier for the user 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 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 force hot water into the grounds, and are far more portable than electric espresso maker steam-driven machines.