How Does Machine Espresso Work?
The machine espresso is made using precise pressure and filtering technology that is amazing to create the coffee you enjoy. How exactly does it work?
Espresso is made by pushing hot water under pressure through finely-ground coffee. The process is similar to making drip coffee but the difference is in the pressure.
The Group Head
The name implies, the group head is the place you insert your portafilter when making espresso. It disperses the water into the portafilter and regulates the pressure during the extraction. There are a variety of group heads each with distinct advantages and disadvantages. Some focus on temperature stability, others on pre-infusion features, and others are designed to control the lever. There are also some that come with a range of features, like the E61 that is the classic choice among many baristas due to its ability to provide multiple benefits in a single package.
As you can see in the photo above, the group head has numerous notches that you can place your portafilter and twist it by hand to lock it in. A gasket of rubber is situated in the notches to create a seal as you insert your portafilter. The notches permit an exact placement of the portafilter. This is vital for an efficient extraction.
The group head is not just able to allow the portafilter to be inserted easily however it also keeps a constant temperature. It does this by cycling hot water through the brew basket, and around the portafilter, making sure that it is always at the right temperature for extraction. This is vital, because even a few degrees can make the difference between good and great espresso.
The Pump
Unlike manual piston machines, which rely on a lever to pressurize water, rotating espresso machines rely upon motorized pumps to provide the nine atmospheric bars of pressure necessary to extract espresso. This pressure is built up by pumping water through a heat exchanger and then through the ground coffee.
Pumps tend to be less expensive than piston-driven machines and tend to last longer. However, both types of machines may be damaged by excessive use and inadequate cleaning. They also make mechanically complex which can result in costly prices for even the simplest models.
Certain espresso machines utilize steam pressure instead of a pump to brew espresso. The drawback 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 these machines are often required to rebuild their pressure between cups, which requires time and energy.
A large majority of espresso machines employ a rotary or vibration pump. A vibration model makes use of a rotating disk to generate pressure, whereas the rotating model pushes hot water through the ground at a high speed. Both types of machine are capable of producing excellent espresso, however rotary machines are quieter and more durable than vibration pumps.
The Boiler
The boiler is the element that heats the water to the ideal temperature for extraction. The resulting steam is then transferred to the portafilter that contains the ground espresso and is then funneled down into the cup. The steam causes pressure to push through the coffee grounds. This creates a foam on top of the espresso. This is the hallmark of a great espresso.
There are three kinds of espresso makers. They differ in the type of pump they employ and how hot the espresso is. There are different ways in which the brew can be controlled as well as the size of the cup the machine is capable of making.
The first espresso machines were steam-type. The first espresso machines were steam types. The coffee tasted bitter and burned. The modern espresso machine was invented by the Milanese makers Luigi Bezzerra & Desiderio Pavoni.
The most popular espresso maker is a semiautomatic machine with an electric pump. These are the images people have when they think of an espresso maker. Semi-automatic machines require you to grind and tamp the beans yourself however the pump controls the flow of water and pressure. This is an excellent compromise between human touch and mechanized quality.
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 element of the machine's temperature control, as it helps prevent overheating.
It also aids in flavor as a filter lets you enjoy a longer bloom time. This allows beans to release their nuances and gives an opportunity for a better extraction.
However it is crucial to remember that even a great filter can produce a bad cup of coffee, because the quality of the beans and extraction are crucial.
9 bar espresso machine is where the magic happens. It's what makes an espresso really taste great. The grouphead (also known as the brewhead) is where you put the portafilter, the device that you put the grounds of your coffee into when making espresso.
Steam-driven espresso machines use hot water that is heated inside an airtight container to make steam. The steam then pushes hot water through grounds of the coffee under pressure. These kinds of machines are typically cheaper and easier to maintain than pumps-driven models. They are however limited in their ability 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, espresso machines driven by a compressed air pump have become increasingly popular. They use an air-compressor to push hot water across the ground and are much more mobile than steam-driven electric espresso machines.