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How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to create the perfect cup of coffee. But how exactly does it work?

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

The Group Head

The group head is the portafilter you insert when brewing espresso. It is responsible for dispersing the water into the portafilter and controlling the pressure that results from the extraction. There are a variety of group heads each with their own advantages and drawbacks. Some are focused on temperature stability, some on pre-infusion capabilities, while others are designed to control the lever. Some include a combination like the E61. This is a very popular choice for baristas since it provides multiple advantages in one package.

As you can see from the photo above the head of the group has a number of notches. The portafilter is placed in these notches, then twist the head to secure it. There is also a gasket of rubber in the notches, which helps create the seal when you insert your portafilter into the machine. The notches allow for an exact placement of the portafilter. This is vital for an accurate extraction.

The group head is not just able to allow you to place your portafilter easily however, it also keeps the temperature at a constant level. This is achieved by cycling hot water around the portafilter, and through the brew-basket to ensure that the temperature is at the right level to extract the coffee. It is crucial to keep in mind that even a slight deviation can make the difference between a good and excellent espresso.

The Pump

The motorized pumps that are used in rotary espresso machines provide the nine atmospheric bar pressure needed to extract espresso. This differs from manual piston machines which use levers. The pressure builds 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 generally less expensive 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, and can add to the cost of even most basic models.

Some espresso machines use steam pressure instead of a pump to brew 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 could lead to excessive extraction. Additionally the machines often have to rebuild their pressure between cups, which requires time and energy.

A large majority of espresso machines employ either a vibration or rotary pump. A vibration model uses an oscillating disk to create pressure, while the circular model pushes hot liquid through the ground at high speed. Both machines can produce excellent espresso however rotary machines tend to be quieter, more durable and less likely to fail.

The Boiler

The boiler is the part that heats the water to the optimal temperature to extract. The resultant steam then reaches the portafilter which holds the ground buy espresso machine coffee, and gets funnelled down into the cup. During this process the steam causes enough pressure to push the coffee grounds through. This results in a whipped-up the top of the espresso. This is one of the hallmarks of a great Best Espresso Machine Under 500.

There are three distinct types of espresso machines, each having a different type of pump and brew temperature. There are a variety of ways to control the brew as well as the size of the cup that can be produced by the machine.

The first espresso machines were steam-types. They employed one boiler to make both steam and brew however, the pressure they could create was minimal - two bars of atmospheric pressure at most. This led to the coffee tasting bitter and burnt. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso machine is a semiautomatic with an electric pump. When people think of espresso machines, they envision these machines. With a semi-automatic machine, you grind the beans and tamp them by hand, but the pump provides regulated water flow and pressure. This is a great compromise between the human touch and mechanized accuracy.

The Filter

Typically, espresso machines use a filter to separate out the grounds of the coffee as they go through the hot water. The filter is also a crucial element of the temperature control system as it prevents the machine from overheating.

Filters also aid in flavor as it allows for a longer flowering phase. This allows beans to let their nuances out and provides an opportunity for better extraction.

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

It's here that the magic happens. This is the reason why buy espresso machine tastes so good. The grouphead, often called the brew head, is the place where the portafilter (the thing you put the coffee grounds into) is placed when making italian espresso machines.

Steam-driven espresso machines make use of hot water that is heated in an airtight container to produce steam. The steam then pushes hot water through grounds of coffee at high pressure. These types of machines are generally less expensive and simpler to maintain than pumps-driven models. However, they are limited in their ability to provide the ideal brewing conditions, as they only operate at 1-1.5 bars of pressure. The perfect shot requires 9-10 bar.

In recent years, compressed air pump-driven espresso machines have become more popular. They utilize an air compressor to force hot water into the grounds, and are far more portable than steam-driven electric machines.