9 Things Your Parents Taught You About Machine Espresso

How Does Machine Espresso Work?

The machine espresso uses precise pressure, as well as a filtering technology that is amazing to create the coffee you enjoy. What exactly does it work?

To make espresso, hot water is forced under high pressure through finely ground coffee. The process is similar to that of making drip coffee. However the pressure is the major difference.

The Group Head

The group head is the portafilter that you put in when making espresso. It disperses water in the portafilter, and regulates the pressure of extraction. There are a variety of types of group head, each with their unique advantages and drawbacks. Some are designed for temperature stability while others are specifically designed to handle pre-infusion. Others are made to control the lever. Some are a combination, like the E61. This is a very popular choice for baristas because it offers multiple advantages in one package.

As you can see in the above photo the group head is made up of many notches in which you can place your portafilter and twist it by hand to lock it in. A rubber gasket is located in the notches to create a seal as you insert your portafilter. The notches on the head permit a precise placement of the portafilter, which is essential to ensure a consistent extraction.

Aside from allowing you to easily insert your portafilter, the group head is responsible for maintaining a consistent temperature. This is achieved by cycling hot water around the portafilter, and through the brew-basket, making sure that the temperature is always at the right level to extract the coffee. It is crucial to keep in mind that even a few degree variation can mean the difference between a great and a great espresso.

The Pump

Unlike manual piston machines, which use a lever to pressurize water, rotating espresso machines rely upon motorized pumps to deliver the nine atmospheric bars of pressure needed to extract espresso. The pressure builds by removing tap water from a reservoir, and pumping it through a heat exchanger prior being shot through the ground coffee in the group head.

Pumps are generally less expensive than piston-driven machines, and tend to last longer, however both types of machines can degrade with overuse and insufficient cleaning. Pumps are also more complicated mechanically, which can increase the cost of even simplest models.

Some espresso machines remove the pump completely and instead employ steam pressure to create espresso. The drawback is that the same boiler that produces steam also raises the temperature of the water to the point of boiling which can cause over-extraction. They also have to constantly rebuild their pressure in between cups. This takes energy and time.

Many espresso machines employ either a rotary or vibration pump, with a vibration model using a vibrating disc to generate the pressure, and a rotary model pushing hot water through the grounds at high speed. Both types of machine can make excellent espresso, however Rotary machines are quieter and more durable than vibration pumps.

The Boiler

The boiler is the one that makes the water warm to a temperature that is ideal to extract. The resulting steam is then transferred to the portafilter, which contains the ground espresso and is then pumped down into the cup. During this process, steam creates pressure to push through the coffee grounds. This creates a crema on top of the espresso. This is a hallmark of a great espresso.

There are three types of espresso makers (super fast reply), which differ in the kind of pump they use and the degree of heat that the coffee is. 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 first espresso machines were steam-types. They employed one boiler to make both steam and brew, but the pressure they could create was minimal - two bars of atmospheric pressure, at most. The coffee tasted bitter and burnt. The modern commercial espresso machine machine was created by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most common espresso maker is a semi-automatic machine that has an electric pump. These are the things people think of when they think of an espresso machine. Semi-automatic machines require you to grind and tamp the beans on your own The pump, however, regulates the flow of water and pressure. This is a perfect compromise between human control and mechanised accuracy.

The Filter

Typically, espresso machines employ filters to separate the grounds of coffee as they move through the hot water. The filter is also an important element of the temperature control system, as it prevents the machine from overheating.

Filters also aid in flavor because it allows for an extended flowering time. This allows the beans to let their nuances out, and allows for better extraction.

It is important to remember that even the finest filter can produce a bad cup of coffee. The quality of the beans as well as the extraction, remain crucial.

This is where the magic happens, it's what makes an espresso really taste good. The grouphead, sometimes called the brew head, is the place where the portafilter (the device you put the ground coffee into) sits when you're making espresso.

In a steam-driven espresso machine hot water is heated in an airtight container to produce steam, which then pushes the hot water through the grounds at high pressure. These machines are cheaper and easier for the owner bean to cup espresso machines maintain than pumps-driven models. They are however limited 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, compressed-air-pump-driven espresso coffee maker machines have been gaining popularity. They use an air compressor to force the hot water through the grounds and are more portable than steam-driven electric machines.