How Do Espresso Machines Work?

by Véronique Raymond
espresso machine components

Espresso machines are much more complicated than your standard coffee maker.

While it might be easier to let your barista handle the fancy drinks, you can easily learn how to do it from home with your very own espresso maker.

First, though, you should understand how they operate and what the various components’ functions are.

Whether you’re brand new to espresso or are an espresso enthusiast, knowing how espresso coffee is made will guarantee a great-tasting homemade espresso.

 

What Is Espresso?

Essentially, espresso is a concentrated shot of coffee. Though the drink itself is small, it packs a bigger caffeine punch compared to most average-sized coffees. Espresso is also the base for many other types of coffee drinks like Americanos, Cappuccinos, Lattes, and others. It is an Italian-style coffee drink that has a thicker consistency and a slightly different brew process compared to regular coffee. Instead of using a coarse grind, gravity, and lots of water, espresso uses high pressure, a finer grind, and minimal water.

espresso machine components

Types of Espresso Machines

Manual Espresso Machines

A manual espresso machine does not have any electric features. It requires the brewer to manually apply pressure using a lever to make espresso. You are responsible for determining the brew length and volume, grinding your own beans, and tamping pressure. There are two types of manual espresso machines: spring piston machines and direct lever machines.

Spring piston machines are a touch easier to use since the spring does some of the physical work for you. When you push down the lever, the spring will move into position. By releasing the lever, you release the spring which forces the water through the portafilter and through the coffee grounds. Though some of the physical work is done for you, you still have control over pre-infusion and other aspects of the brewing process.

Direct lever machines are the more challenging model but also the one most likely to deliver the best shot of espresso you’ve ever had. By applying direct pressure to the lever, you apply direct pressure to force the water over your coffee grounds. The room for error with this type of manual espresso maker is high, so there is a significant learning curve with this machine.

Automatic Espresso Machines

There are three types of automatic espresso machines: Semi-Automatic Espresso Machines. Automatic Espresso Machines, and Super-Automatic Espresso Machines. Each of these machines offers different levels of autonomy. Here are the main differences:

  • Super-automatic machines have a built-in grinder for coffee beans
  • Semi-automatic machines require you to grind and tamp your beans, load the portafilter, and start the shot
  • Automatic machines are very similar to semi-automatic except they’ll stop the shot at the perfect time
  • Super-automatic machines are all-inclusive: they grind, tamp, run the shot, and even froth milk

Commercial Espresso Machine

Commercial machines are exactly like home espresso machines except they are larger. These machines can cost anywhere from $2000 to more than $40,000 for a top-of-the-line model. Most are super-automatic for efficiency, and they come with all the accessories a commercial coffee shop would need for espresso drinks.

 

How Do Espresso Machines Work?

Manual grinders excluded, nearly every model of espresso machine operates the same way using the same components. While some models will vary, the basic process is the same. Espresso machines need pressure from pumps, pistons, or steam, a water source, a heating element, tamped down coffee beans, a single boiler or dual boiler, a portafilter, a filter basket, and sometimes a milk frother.

Components Explained

espresso machine components

Group Head

The group head is also known as the brew head. It is the heart of the machine. The group head holds the portafilter and is responsible for sending heated, pressurized water through a diffusion plate and into the coffee grounds held in the portafilter. Then, the water flows through the nozzles at the bottom into your mug.

Steam Wand/Steam Chamber

The steam wand is an essential piece of equipment for espresso drinks that use milk. To heat the milk to the right temperature, you need steam. Many models, especially dual boiler models, will have a steam wand built in. In many cases, you can purchase it separately as well. In single boiler machines, the steam wand cannot be used at the same time as you make an espresso shot since steam requires boiling and espresso doesn’t. Steaming milk with a wand on your espresso machine is more convenient than using a second piece of equipment.

Types of Pumps

There are two types of electric pumps in espresso coffee machines, and they work a little differently from each other.

Vibratory Pumps

This type of pump uses a spring and piston design that vibrate to create pressure. They easily reach 9 bars of pressure. This type of pump is cheaper and doesn’t last as long. Plus, it is the louder of the two during operation.

Rotary Pumps

The second type of pump is the rotary pump. Though more expensive, it can last a lifetime and is much quieter to operate. As the name suggests, this type of pump creates pressure by spinning a gear-like mechanism. Their main benefit over vibratory pumps is that they can be used with a water reservoir as well as with a direct water line: vibratory pumps can only work with a reservoir.

Portafilter

The portafilter is a basket that sits in the brew head and holds your coffee grounds. It locks into the group head so it doesn’t fall off when the espresso is extracted. Depending on the size of the portafilter, it will have one or two spouts that help the espresso flow evenly. This is especially important when pulling double shots for two cups. Some portafilters will have a pressure gauge built in, but this is more common on commercial machines.

espresso machine components

Types of Boilers

Single Boiler

In a single boiler espresso machine, there is only one boiler for both steaming with the wand and extracting your espresso. Since these two activities take place at different temperatures, you’ll have to do your steaming second with a steam setting on your espresso maker. Single boiler models are not ideal if you’ll be making multiple drinks with milk in a row, but they are the more affordable option.

Dual Boiler

Dual boiler espresso machines have two boilers: one for extraction and one for steaming. The temperatures for these two activities can be individually set, and there is no need to wait for temperature changes between tasks or drinks since it can heat water to the two different water temperatures you need simultaneously.

Heat Exchanger

The heat exchanger is another option. Though it also has a single boiler, it operates a little differently. The boiler maintains the high temperature needed for steaming, but the water that is being used for a shot pulls water through a tube that lowers the temperature for perfect extraction below boiling. After you pull a shot, you’ll need a cooling shot since the boiling water for steam will make any leftover shot water continue to heat. To avoid hot water in your next shot, it needs to be flushed out first since. The downside to this system, in addition to the extra step, is that you can’t control your brewing temperature very well, if at all.

Filter Basket

The filter basket in your portafilter controls how much coffee grounds it can hold. There are many size options available with the most common being one shot or two shots of espresso, or between 14 and 24 grams of espresso respectively.

Water Reservoir vs. Plumbed System

In terms of a water source, there are two different setups for an espresso machine. The basic option is the water reservoir. This works exactly like a normal coffee machine in that you add a certain amount of water to the tank manually. A plumbed system is an external setup that connects to the main water pipe for your kitchen and sends water first through a filter and softener before reaching your espresso machine. Most domestic brewers won’t need a plumbed system unless they make numerous espresso drinks every day and want more convenience.

Grinder

To make espresso, you need finely ground coffee beans. However, there is some leeway, so you can make a custom grind size with the right grinder since most built-in grinders have many ground size options to choose from. The grinder on your espresso machine adds the grounds directly to the portafilter to save you an extra step when brewing.

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