How Does Machine Espresso Work?

Machine espresso uses precision pressure and Coffeee amazing filter technology to make the coffee we love. What exactly is it that makes it work?

To make an espresso hot water is forced under high pressure through finely ground coffee. The process is similar to making drip coffee, but the key difference is in the pressure.

The Group Head

As the name suggests the group head is where you insert your portafilter when making espresso. It disperses water in the portafilter, and regulates the pressure of the extraction. There are several different types of group heads each with its own advantages and disadvantages. Some are designed to provide the stability of temperature while some are designed to handle pre-infusion. Others are made to control the lever. Some have a combination of features, like the E61, which is the classic choice among many baristas for its ability to offer multiple perks in one package.

As you can see in the above image the group head comes with several notches where you place your portafilter before twisting it manually to lock it in. A gasket of rubber is situated inside the notches to help make a seal when you insert your portafilter. The notches permit an exact placement of the portafilter. This is vital for an accurate extraction.

In addition to allowing you easily insert your portafilter, the group head is also responsible for maintaining an even temperature. It does this by cycling hot water through the brew basket and around the portafilter to ensure that it is always at the right temperature to extract. It is important to remember that even a few degree variation can mean the difference between a great and a excellent espresso.

The Pump

Motorized pumps in rotary espresso machines provide the nine atmospheric bars of pressure required to extract espresso. This is different from manually operated piston machines that employ levers. This pressure builds up by drawing tap water from a reservoir, and pumping it through a heat exchanger before being pushed through the ground coffee in the group head.

Pumps are generally more affordable and last longer than piston-driven machines. However, both kinds of machines are susceptible to degrading due to excessive use and insufficient cleaning. They also make mechanically complex that can lead to a high price tag on even the simplest models.

Some espresso machines remove the pump entirely and make use of steam pressure to make espresso. The drawback of this is that the boiler that produces steam also raises the temperature of water to the point of boiling and can result in over-extraction. The machines must also continuously rebuild their pressure between cups. This requires energy and time.

A large majority of espresso machines employ a rotary or vibration pump. A vibration model uses the vibrating disk to create pressure, while a rotary model pushes hot water through the ground at high speed. Both machines can make great espresso, but rotary machines are more quiet, durable and less likely to break.

The Boiler

The boiler is what makes the water warm to the right temperature for extraction. The resulting steam is then transferred to the portafilter, which contains the ground espresso coffee, and is then pumped into the cup. During this process the steam is able to create enough pressure to push the grounds of coffee through. This results in a layer crema on top. This is one of the hallmarks of a good espresso.

There are three distinct types of espresso machines, each having distinct pumps and the temperature of the brew. There are different ways that the brew can be controlled and the dimensions of the cup the maker can create.

The first espresso machines were steam-type. They utilized one boiler to make steam and brew, but the pressure they could generate was low - only two bars of atmospheric pressure, at most. The coffee tasted bitter and burned. The modern espresso machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most well-known espresso maker is a semiautomatic machine that has an electric pump. These are the images people have when they imagine an espresso machine. With a semi-automatic machine you must grind the beans and then tamp them yourself but the pump regulates the flow of water and pressure. This is an excellent compromise between human touch and the mechanised quality.

The Filter

Espresso machines usually use a filter that separates the grounds of the coffee from the hot water. The filter is also a vital part of the temperature control system since it helps prevent the machine from overheating.

It also enhances flavor, since a filter allows for a longer bloom time. This lets the beans let their nuances out, Coffeee and also allows for better extraction.

It is important to remember that even the most efficient filter could result in a poor cup of coffee. The quality of the beans, as well as the extraction, are still very important.

It's here that the magic takes place. This is what makes espresso taste so delicious. The grouphead, sometimes referred to as the brew head, is the place where the portafilter (the device you put the ground coffee into) is placed when making espresso.

Steam-driven espresso coffee maker machines make use of hot water that is heated inside an airtight vessel to create steam. The steam then pushes hot water through the grounds of coffee under high pressure. These types of machines tend to be less expensive and simpler to maintain than pump-driven models. They are however limited in their ability for creating 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 powered by a compressed air pump have become increasingly popular. They use an air-compressor to force hot water into the ground, and are more mobile than electric steam-driven espresso machines.