9 . What Your Parents Taught You About Machine Espresso

How Does Machine Espresso Work?

Machine espresso employs precise pressure and mind-blowing filter technology to create the delicious coffee we enjoy. But how exactly does it work?

To make espresso, hot water is pushed under pressure through finely ground coffee. The process is similar to making drip coffee. However the pressure is the main difference.

The Head of the Group

The name implies the group head is the place you place your portafilter when brewing espresso. It is responsible for dispersing water into the portafilter and then controlling the pressure of the resulting extraction. There are a variety of group heads each with their own advantages and disadvantages. Some are focused on temperature stability, while others on pre-infusion options, and others are designed to control the lever. Some include a combination like the E61. This is a popular choice among baristas since it provides multiple advantages in one package.

As you can see in the photo above the group head is fitted with several notches. You place your portafilter inside these notches, and then twist the head to lock it. A gasket made of rubber is placed inside the notches to help create a seal when you insert your portafilter. The notches on the head permit an exact positioning of the portafilter which is essential for an even extraction.

In addition to allowing you to easily connect your portafilter, the group head is responsible for maintaining a consistent temperature. This is accomplished by cycling hot water around the portafilter, and through the brew-basket, ensuring that the temperature is at the right level to extract the coffee. It is important to remember that even a slight variation can mean the difference between a decent and a great espresso.

The Pump

Contrary to manual piston machines which use a lever to pressurize water, Rotary espresso machines rely on motorized pumps to supply the nine atmospheric bars of pressure required for espresso extraction. The pressure is created by pumping water through a heat-exchanger and then through the ground coffee.

Pumps are generally less expensive than piston-driven models, and they tend to last longer, however both types of machines can be damaged by excessive use and inadequate cleaning. Pumps are also more complex mechanically, which could increase the price of even the simplest models.

Some espresso machines make use of steam pressure instead of a pump to brew espresso. This can result in over-extraction because the boiler that makes steam also heats the water to boil. They also have to continuously rebuild their pressure between cups. This takes energy and time.

Many espresso coffee machine with milk frother machines make use of a rotary or vibration pump. A vibration model utilizes an oscillating disk to create pressure, whereas a Rotary model pushes hot coffee through the ground at a fast speed. Both machines can produce excellent espresso but rotary machines are quieter, more durable and less likely to break.

The Boiler

The boiler is what makes the water warm bean to cup espresso machine the ideal temperature to extract. The steam that is created reaches the portafilter, which holds the espresso grounds. It is then poured into the cup. During this process, steam causes pressure to push through the coffee grounds. This results in a crema on the top of the espresso. This is one of the hallmarks of a great espresso.

There are three distinct types of espresso machines, each with different pumps and the temperature of the brew. There are a variety of ways in which the brew can be controlled and the size of the cup the machine can produce.

The earliest espresso machines were steam types. They had only one boiler to make steam and brew, but the pressure they could produce was not very high - two bars of atmospheric pressure at the most. This led to the coffee tasting bitter and burnt. The modern espresso machine was developed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso maker is a semi-automatic device that has an electric pump. These are the things people think of when they imagine an espresso machine. Semi-automatic machines require you to grind and tamp the beans yourself The pump, however, regulates the flow of water and pressure. This is an excellent combination of human control and mechanized accuracy.

The Filter

Espresso machines typically use filters that separate the grounds of the coffee from the hot water. The filter is also a vital part of the temperature control system as it keeps the machine from overheating.

A filter can also help with flavor since it allows for a longer flowering phase. This allows beans to release their nuances and gives an opportunity for better extraction.

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

This is where the magic happens, and it's what makes an espresso really taste great. The grouphead (also called the brewhead) is where you put the portafilter, the device which you put the coffee grounds in, while making espresso.

In an espresso machine that is driven by steam, hot water is heated in an airtight container to create steam, which then pushes the hot water through the grounds at a high pressure. These types of machines are usually less expensive and easier to maintain than pump-driven models. However, they are limited in their ability to create the ideal conditions for brewing since they are only operating at 1-1.5 bars of pressure. However, the perfect shot requires 9-10 bar.

In recent times, espresso machines powered by compressed air-pump are becoming increasingly popular. They make use of an air compressor to force hot water through the ground and are much more mobile than electric steam-driven espresso machines.