A Good Rant About Machine Espresso

How Does Machine Espresso Work?

Machine espresso uses precision pressure and incredible filter technology to produce the perfect cup of coffee. What exactly does it work?

Espresso is made by pushing hot water under high pressure through finely ground coffee. The process is similar to making drip coffee. However, it is the pressure that makes the main difference.

The Group Head

The name implies, the group head is where you put your portafilter in when brewing espresso. It disperses water into the portafilter, and then regulates the pressure of the extraction. There are a variety of group heads each with their own advantages and disadvantages. Some are designed for stability of temperature while others are built to handle pre-infusion. Others are built to control the lever. There are even some that include a mix of features, such as the E61, which is considered to be the most popular among baristas because of its ability to offer multiple benefits in one package.

As you can see from the above photo the group head is fitted with a variety of notches. You place your portafilter in these notches and then turn the head around to secure it. A gasket made of rubber is placed in the notches to make a seal when you insert your portafilter. The notches on the head permit a precise positioning of the portafilter which is vital for a consistent extraction.

In addition to allowing you easily insert your portafilter, the group head is also responsible for maintaining a consistent temperature. It does this by cycling hot water through the brew basket, and around the portafilter to ensure that it's always at the right temperature for extraction. This is important, as just a few degrees could make the difference between excellent and great espresso.

The Pump

In contrast to manual piston machines which rely on a lever that pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure that are required to extract espresso. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally less expensive and last longer than piston-driven machines. However, both kinds of machines may degrade due to overuse and poor cleaning. Pumps are also more complicated mechanically, which could increase the price of even the most basic models.

Certain espresso machines eliminate the pump completely and employ steam pressure to create espresso. This can cause over-extraction because the boiler that produces steam also heats the water to boil. The machines must also constantly rebuild their pressure between cups. This requires energy and time.

Many espresso machines utilize the rotary or vibration 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 models can make a great espresso, but Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the component that heats water to the optimal temperature for extraction. The steam that is produced gets to the portafilter which is a container for espresso grounds. It is then funneled into the cup. During this process the steam is able to create enough pressure to push the coffee grounds through. This results in a crema on top of the espresso. This is a hallmark of a good espresso.

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

The earliest espresso machines were steam types. They had a single boiler to make both brew and steam, however the check here pressure they were able to produce was not very high - two bars of atmospheric pressure at the most. The coffee tasted bitter and burnt. The modern espresso machine was invented by the Milanese producers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso maker is a semi-automatic machine with an electric pump. When people think of espresso machines, they think of these machines. Semi-automatic machines require you to grind and tamp the beans by yourself however the pump controls the water flow and pressure. This is an excellent compromise between human touch and mechanized accuracy.

The Filter

Typically, espresso machines have a filter to separate out the grounds of coffee when they pass through the hot water. The filter is also an essential component of the machine's temperature control, since it helps to prevent overheating.

Filters also aid in flavor as it allows for an extended flowering time. This allows beans to release their flavors and provides the chance for better extraction.

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

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

Steam-driven espresso machines use hot water that is heated in an airtight vessel to create steam. The steam then moves hot water through the grounds of coffee under high pressure. These types of machines tend to be less expensive and easier to maintain than pumps-driven models. However, they are limited in their ability to create the ideal brewing conditions, since they are only operating at 1-1.5 bars of pressure, while the perfect shot requires 9-10 bar.

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