How Does Machine Espresso Work?

Machine espresso makes use of precise pressure and amazing filter technology to make the delicious coffee we enjoy. But how exactly does it work?

Espresso is made by pushing hot water under high pressure through finely ground coffee. The process is similar to 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 into the portafilter and controls the pressure of the extraction. There are several different types of group head, each with their distinct advantages and disadvantages. Some are designed to provide stability of temperature while others are specifically designed to handle pre-infusion. Others are built to control the lever. Some come with a range of features, like the E61, which is the standard choice for many baristas due to its capacity to offer multiple benefits in one package.

As you can see in the image above The group head features many notches in which you can place your portafilter and then twist it with your hands to secure it. A gasket made of rubber is positioned within the notches to create a seal when you insert your portafilter. The notches on the head allow for an exact location of the portafilter which is essential to ensure an efficient extraction.

The group head is not just able to allow you to place your portafilter easily however it also keeps a constant temperature. It does this by circulating hot water through the brew basket and around the portafilter, ensuring that it is always at the right temperature for extraction. It is important to remember that even a few degree variation can mean the difference between a decent and a excellent espresso.

The Pump

The motorized pumps used in espresso machines rotary provide nine atmospheric bars of pressure required to extract espresso. This differs from manual piston machines which use levers. The pressure is built by pumping water through a heat-exchanger and then through the ground coffee.

Pumps tend to be less expensive than piston-driven models, and they tend to last longer, although both types of machines can become damaged due to excessive use and poor cleaning. Pumps are also more complex mechanically, which can raise the cost of even the simpler models.

Some espresso machines espresso machines use steam pressure instead of a pump to brew espresso. The downside is that the boiler that produces steam also increases the temperature of water until it reaches boiling which could lead to excessive extraction. The machines also need to constantly rebuild their pressure in between cups. This requires energy and time.

Many espresso machines employ either a rotary or vibration pump, with a vibration model using a vibrating disc to create the pressure and the rotary model pushing hot water through the grounds under high speed. Both machines produce great espresso, however rotary machines are more quiet, durable and less likely to break down.

The Boiler

The boiler is what is used to heat the water to a temperature that is ideal for extraction. The steam produced reaches the portafilter, which is the container that holds the espresso home machine coffee grounds. The steam is then channeled into the cup. During this process the steam generates enough pressure to push the grounds of coffee through. This produces a layer of crema on top. This is one of the hallmarks of a great espresso.

There are three types of espresso makers. They differ in the type of pump they employ and the degree of heat that the espresso is. There are various ways to control the brew and the size of cup that can be made by the machine.

The first espresso machines were steam-types. They employed a single boiler to make steam and brew, but the pressure they could produce was very low - just two bars of atmospheric pressure at most. The coffee tasted bitter and burned. The modern espresso machine was designed by the Milanese manufacturers Luigi Bezzerra & Desiderio Pavoni.

The most popular espresso machine is a semiautomatic model 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 on your own while the pump controls the flow of water and pressure. This is a perfect compromise between human control and mechanized consistency.

The Filter

Espresso machines typically have filters that separate the grounds of the coffee from the hot water. The filter is also an important component of the temperature control system as it prevents the machine from overheating.

It also improves flavor, as a filter allows for a longer bloom phase. This allows the beans to release their nuances, and allows for better extraction.

However, it is important to remember that even a high-quality filter can result in a poor cup of coffee as the quality of the beans and extraction is still important.

It's here that the magic occurs. This is the reason why espresso tastes so delicious. The grouphead, often called the brewhead, is where the portafilter (the thing you put the ground coffee in) is located when you're making espresso.

In an italian espresso machines machine that is driven by steam, hot water is heated in an airtight container to create steam. This is then pushed through the grounds 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 brewing conditions as they only operate with 1-1.5 bar of pressure. The ideal shot requires 9-10 bars.

In recent years, compressed air-driven espresso machines have been gaining popularity. They use an air compressor to force the hot water through the grounds, and are far more portable than electric steam-driven machines.