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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to make the delicious coffee we enjoy. What exactly is it?

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 Group Head

As the name suggests, the group head is the place you put your portafilter in when brewing espresso. It is responsible for dispersing the water into the portafilter, and controlling the pressure of the resulting extraction. There are many different types of group heads each with their own advantages and disadvantages. Some are designed for temperature stability while others are designed to handle pre-infusion. Some are designed to control the lever. Some contain a variety of features, such as the E61 one, which is the standard choice for many baristas due to its ability to offer multiple perks in one package.

As you can see in the above image the group head comes with several notches where you place your portafilter before twisting it by hand to lock it in. A gasket of rubber is situated within the notches to create a seal when you insert your portafilter. The notches permit an exact placement of the portafilter. This is vital for an even extraction.

Apart from allowing you effortlessly insert your portafilter the group head is responsible to maintain an even temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is always at the right level for extraction. This is important because even a small difference in temperature can make the difference between a good and great espresso.

The Pump

The motorized pumps used in espresso machines that rotate provide the nine atmospheric bar pressure that is required for espresso extraction. This differs from manual piston machines which use levers. This pressure builds up by drawing tap water from a reservoir and pumping it through a heat exchanger prior to being pushed through the ground coffee in the group head.

Pumps tend to be cheaper than piston-driven machines, and tend to last longer, although both types of machines could be damaged by excessive use and inadequate cleaning. Pumps are also more complicated mechanically, and can add to the price of even the simple models.

Certain espresso machines do away with the pump entirely and employ steam pressure to create espresso. This can cause over-extraction because the boiler that makes steam also heats the water until it comes to a boil. Additionally these machines typically have to restore their pressure between cups, which takes time and energy.

Many espresso machines make use of an rotary or vibrating pump, which has a vibration model using a vibrating disc that generates the pressure, and the rotary model pushing hot water through the grounds under high speed. Both machines can produce excellent espresso, however rotary machines are more quiet, durable and less likely to fail.

The Boiler

The boiler is what makes the water warm to the right temperature for extraction. The steam produced will eventually reach the portafilter, which is the container that holds the espresso coffee grounds. It is then pumped into the cup. In this process, the steam creates pressure to push through the coffee grounds. This creates a layer crema on top. This is the hallmark of a good espresso.

There are espresso machines uk of espresso makers. They differ in the kind of pump they use and the degree of heat that the espresso is. There are a variety of ways to control the brew and the size of the cup that can be made by the machine.

The earliest espresso machines were steam type. They used one boiler to create both steam and brew but the pressure they could create was minimal - two bars of atmospheric pressure at most. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso maker is a semi-automatic machine with an electric pump. These are the things people think of when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans on your own while the pump controls the water flow and pressure. This is a great compromise between the human touch and the mechanised accuracy.

The Filter

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

It also helps with flavor, since a filter can allow for a longer bloom phase. This helps the beans to release their flavors 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 as well as the extraction, remain crucial.

This is where the magic happens, and it's what makes espresso taste great. The grouphead (also called the brewhead) is where you place the portafilter, the device which you put the coffee grounds into, while making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam. This then pushes the hot water through the grounds at high pressure. They are less expensive and are easier for the user to maintain than pumps-driven models. They are however limited in their ability for creating 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 powered by a compressed air compressor have become increasingly popular. They use an air compressor to force hot water through the grounds, and are far more portable than steam-driven electric machines.