How Does Machine Espresso Work?

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

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

The Group Head

As the name implies the group head is the place you place your portafilter when making espresso. It disperses water into the portafilter, and then regulates the pressure of the extraction. There are many different types of group heads, each with its own advantages and disadvantages. Some are designed to provide temperature stability while others are designed to handle pre-infusion. Others are built to control the lever. Some have a combination, such as the E61. This is a favorite among baristas since it provides multiple advantages in a single package.

As you can see in the image above The group head features several notches where you place your portafilter and then twist it manually to lock it in. There is also a gasket of rubber in the notches and helps create the seal when you insert your portafilter into the machine. The notches permit the precise placement of the portafilter. This is essential for an efficient extraction.

Aside from allowing you to easily place your portafilter in, the group head is also responsible to maintain an even temperature. It does this by cycling hot water through the brew basket and around the portafilter, making sure that it's always at the right temperature to extract. This is crucial, since just a few degrees could make the difference between good and great espresso.

The Pump

In contrast to manual piston machines which rely on a lever that pressurize water, Rotary espresso machines rely on motorized pumps to provide the nine atmospheric bars of pressure required to extract espresso. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.

Pumps are generally less expensive and last for longer than piston-driven machines. However, both types of machines are susceptible to degrading because of frequent use and inadequate cleaning. Pumps are also more complicated mechanically, which can increase the price of even the simple models.

Some espresso machines use steam pressure instead of a pump for brewing best espresso machine under 500. This could lead to over-extraction since the boiler that makes steam also causes the water to boil. The machines also need to constantly rebuild their pressure between cups. This takes energy and time.

Many mini Espresso machine (willysforsale.com) machines use a rotary or vibration pump. A vibration model utilizes a rotating disk to generate pressure, while a circular model pushes hot liquid through the ground at a high speed. Both types of machine can make a great espresso, but the rotary pumps are quieter, and more durable than vibration pumps.

The Boiler

The boiler is the part which heats the water to the ideal temperature for extraction. The steam created gets to the portafilter which is the container that holds the espresso coffee grounds. It is then poured into the cup. The steam generates enough pressure to push the coffee grounds through. This results in a whipped-up the top of the espresso. This is a hallmark of a good espresso.

There are three kinds of espresso machines, each with different pumps and brew temperature. There are different ways in which the brew could be controlled, as well as the dimensions of the cup the machine can produce.

The first espresso machines were steam-types. They utilized only one boiler to make both brew and steam, but the pressure they could produce was not very high - two bars of atmospheric pressure maximum. This led to the coffee tasting bitter and burnt. This is why Milanese manufacturers Luigi Bezzerra and Desiderio Pavoni developed the modern espresso machine.

The most commonly used espresso maker is a semi-automatic machine with an electric pump. These are what people imagine when they think of an espresso machine. 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 accuracy.

The Filter

Espresso machines typically use filters that separate the coffee grounds from the hot water. The filter is also an essential element of the machine's temperature control, as it helps prevent overheating.

It also aids in flavor as a filter allows for a more prolonged bloom phase. This allows the beans to release their flavor and allows for better extraction.

It is important to remember that even the best espresso maker filter can produce a bad cup of coffee. The quality of the beans as well as the extraction, are still crucial.

It's in this area that the magic takes place. This is the reason why espresso tastes so good. The grouphead, often called the brew head, is where the portafilter (the thingy you put the coffee ground into) is placed when making espresso.

Steam-driven espresso machines use hot water that is heated inside an airtight container to make 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 simpler to maintain than pumps-driven models. They are however limited in their ability for creating the ideal conditions for brewing, as they operate with 1-1.5 bar of pressure. The perfect shot requires 9-10 bars.

In recent years, espresso machines powered by compressed air-pump are becoming increasingly popular. They utilize an air compressor to push the hot water through the grounds and are significantly more portable than electric steam-driven machines.