How Does Machine Espresso Work?

Machine espresso uses precision pressure and mind-blowing filter technology to make the perfect cup of coffee. But how exactly does it work?

Espresso is created by forcing hot water at high pressure through finely-ground coffee. The process is similar to making drip coffee, but the major difference is in the pressure.

The Group Head

The name implies the group head is the place you place your portafilter while making espresso. It disperses the water into the portafilter, and regulates the pressure of the extraction. There are a variety of group heads, each with its own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion features, and others are designed to control the lever. Some are a combination, like the E61. This is a preferred choice for baristas as it provides a variety of benefits in one package.

As you can see in the picture above, the group head is equipped with several notches. The portafilter is placed in these notches, then twist the head to lock it. There is also a rubber gasket that resides inside the notches to help create a seal when you insert your portafilter into the machine. The notches on the head allow for a precise location of the portafilter which is essential for a consistent extraction.

Aside from allowing you to easily insert your portafilter, 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 to ensure that it is always at the correct temperature for extraction. It is important to note that even a tiny differences can make the distinction between a good and a great espresso.

The Pump

Motorized pumps in espresso machines rotary provide nine atmospheric bar pressure required to extract espresso. This is different from manual piston machines which use levers. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.

Pumps are generally less expensive than piston-driven machines and tend to last longer, however both types of machines can degrade with overuse and insufficient cleaning. Pumps are also more complicated mechanically, which could increase the cost of even the simple models.

Some retro espresso maker (resources) machines use steam pressure instead of a pump to make espresso. This can cause over-extraction because the boiler that makes steam also heats the water to boil. They also have to constantly rebuild their pressure in between cups. This takes energy and time.

Many espresso machines make use of an rotary or a vibration pump. A vibration model utilizes the vibrating disk to create pressure, whereas the circular model pushes hot liquid through the ground at high speed. Both models can make a great espresso, but the rotary models are quieter and more durable than vibration pumps.

The Boiler

The boiler is the element that heats water to the optimal temperature for extraction. The steam that is produced reaches the portafilter containing 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 creates a foam on top espresso machines of the espresso. This is a hallmark of a great espresso.

There are three kinds of espresso makers. They differ in the type of pump they use and the degree of heat that the espresso is. There are different ways to control the brew as well as the size of cup that can be made by the machine.

The earliest espresso machines were steam type. They employed only one boiler to make steam and brew, however, the pressure they could generate was low - only two bars of atmospheric pressure maximum. This resulted in the coffee tasting bitter and burnt. This is the reason why Milanese producers Luigi Bezzerra and Desiderio Pavoni created the modern espresso machine.

The most well-known espresso maker is a semi-automatic device that has an electric pump. When people think of espresso machines, they envision these machines. Semi-automatic machines require you to grind and tamp the beans by yourself, but the pump regulates the water flow and pressure. This is a great compromise between the human touch and the mechanised consistency.

The Filter

Typically, espresso machines use filters that separate the coffee grounds as they pass through the hot water. The filter is also a vital component of the machine's temperature control, since it helps to prevent overheating.

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

It is important to remember that even the best 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 the thing that makes espresso taste great. The grouphead, also referred to as the brew head, is where the portafilter (the thingy you put the ground coffee into) is placed when making espresso.

Steam-driven espresso machines make use of hot water that is heated inside an airtight container to create steam. The steam then pushes hot water into the grounds of the coffee under 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 ideal shot requires 9-10 bars.

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