How Does An Espresso Machine Work? - HomeGrounds

HOW DO ESPRESSO MACHINES WORK?

Let’s learn how espresso machine works.

You’ve had an espresso machine on your wish list for a while and are finally ready to bring one home. But where do you start? Even if you’re already a drip coffee expert, espresso is a different beast altogether. 

In this guide, I’ll explain exactly how does an espresso machine work, from basic parts to terminology. Not only will the knowledge help you shop with confidence, but it will make you a better barista once you get that shiny new machine home.

Types of Espresso Machines

Modern espresso machines are broadly classified into four categories. They share many commonalities in design and operation but differ in their required user input.

• Super-automatic machines are completely hands-off, usually including an integrated grinder. You press a few buttons and await your espresso.
• Automatic espresso machines control shot timing using a timer or flowmeter to measure the amount of water. But you need to grind, dose, and tamp the coffee grounds.
• Semi-automatic espresso machines require you to start and stop the shot, as well as prepare the coffee puck in the portafilter.
• Manual espresso machines don’t include an electric pump. Along with preparing the ground coffee beans, you must generate the extraction pressure by hand – usually with a lever and/or piston.

Dialing In Your Lingo – Key Terms To Know

Here are a few more key terms to know when discussing espresso machines.

• Dialing in – Dialing in is coffee jargon for tweaking certain parameters of the brewing process to get the perfect espresso. This might entail adjusting the grind size, tamp, or amount of coffee used.
• Portafilter – The portafilter holds the ground coffee. It’s exactly what its name suggests – a metal filter basket with an attached handle for portability.
• Tamp – Tamping is compressing the ground coffee into the portafilter to make a dense puck so that the pressurized water doesn’t pass through the coffee grounds too quickly. A good tamp creates the necessary restriction, prevents water channeling, and helps dissolve more solids (1).
• Bars of Pressure – A bar is a unit of measurement for pressure. Common knowledge suggests that a proper espresso is extracted at 9 bars of pressure, which is 130 PSI — or over four times as much as a car tire (2)!

Now that you’re speaking the language, let’s look at the different parts of your home espresso machine.

Pumps And Water Pressure

You can’t have espresso without water, right? In an espresso machine, the water source is either an attached reservoir or a connected water line. You can find home espresso machines that utilize either.

The first espresso machines used steam pressure to push water through the machine. But these days, unless you use a manual espresso maker, a pump rather than manual force does the work.

Espresso brewing means extracting coffee at high pressure, traditionally 9 bars. A pump creates pressure that forces the flow of water through the coffee.

“Espresso has a long history, and nine bars is known to be the optimal pressure used to extract the best espresso.”

There are two main types of pumps: vibration and rotary pumps. Rotary pumps are more commonly used in commercial espresso machines and provide more consistent pressure. Vibration pumps are smaller and more affordable, making them more common in home machines. Unless you’re really geeking out, you might not notice a difference, except that vibratory pumps tend to be noisier (3).

Heating Elements: Thermoblocks And Boilers

A stable and accurate brew temperature is a crucial aspect of pulling a great shot of espresso. The ideal temperature of the brew water is 195 to 205°F, which espresso machines may achieve using a boiler or thermoblock, depending on the type of machine.

A thermoblock is a hot block of metal inside your espresso machine with a pipe running through it. Water is heated as it runs through the pipe from the reservoir to the group head. Cheaper espresso machines use thermoblocks because they are fast and convenient. Professional machines rely on boilers, which deliver a more accurate and stable water temperature.

All About Boilers

The boilers are some of the most important espresso machine features to consider. Water is fed into the boiler through a one-way valve, where it is collected and heated. There are three main types of boiler designs:

Single Boiler

In a single boiler set-up, water for brewing espresso and steaming milk is collected and heated in one single tank.

The problem with a single boiler is that you cannot brew espresso and use the steam wand simultaneously because the temperatures for steaming milk and brewing espresso are drastically different. You need to wait for the water to heat up or cool down after each process. This is a bit of a pain when you’re trying to make milk-based drinks like lattes and cappuccinos.

Heat Exchange

A heat exchanger is also one large boiler, but it has an isolated section separate from the main heating element. The isolated section provides cooler water suitable for brewing. This is achieved by continuously supplying water through the isolated element, into the group head, and back down into the machine.

The ability to heat water to different temperatures allows you to brew and steam at the same time.

Dual Boiler

Espresso machines with a dual boiler have two separate tanks. One tank heats water for brewing while the other heats water for steaming.

A dual boiler means that you don’t need to wait for the water temperature to change. The two separate boilers allow you to steam milk and brew simultaneously and provide the best option for temperature stability since each tank can be held at the appropriate water temperature.

A dual boiler is the way to go if you’re a dedicated fan of espresso drinks with milk froth.

Related: Dual Boiler vs Heat-Exchanger

The Group Head

Every espresso machine needs a group. This is where the magic happens. It’s the part on the front of your espresso machine where the portafilter locks into place. Most home machines have a single group, while commercial machines in busy coffee shops may have up to four groups.

When you pull an espresso shot, the valve seats open, and the group head sends pressurized, hot water from your espresso machine, through your puck of coffee, and out the bottom of your portafilter, creating espresso.

The most common designs are saturated and semi-saturated group heads – two different ways to ensure the group is hot and a stable brew temperature is maintained.

A saturated group head is essentially an extension of the espresso machine’s boiler. A semi-saturated group is separated from the boiler and plumbing is used to circulate hot water between them.

Final Thoughts

After this look under the hood, you hopefully have a better understanding of how an espresso machine works. Though the process of running hot water through compact coffee sounds simple, there’s a lot going on under the hood to ensure the quality of the espresso.

Your next task? Learning how to make your favorite coffee beverages at home!

Were the inner workings of the espresso machine more complicated than you expected? Or are simpler than you figured? Let us know!

FAQs

Can you use regular coffee for espresso?

Yes, you can use regular coffee beans for espresso, but designated espresso beans are more likely to deliver the extraction and flavor profile you expect for espresso. The coffee grind size is much more important than the type of coffee. You need to use finely ground coffee in an espresso machine, so most pre-ground coffee beans won’t work.

What is the difference between a coffee machine and an espresso machine?

The main difference between a coffee machine and an espresso machine is that an espresso machine uses high pressure whereas drip coffee makers rely on the force of gravity. That’s why the costs of espresso machines are higher. Not only do they require the addition of a pump, but the overall build of the machine must tolerate greater forces.

If you don’t want to shell out for an espresso machine, here’s how to make a strong coffee similar to espresso without a machine.

What’s the difference between coffee and espresso?

The difference between coffee and espresso is how they’re made, which in turn yields different drink styles. Espresso is made quickly, under high pressure, and using fine grinds. The result is a small, concentrated coffee drink with a heavy mouthfeel and layer of crema. Coffee is made slowly, under lower pressure, and with coarser grounds. It has a milder flavor and body and is served in larger quantities.

Can an espresso machine make regular coffee?

No, an espresso machine can’t make regular coffee – with rare exceptions. But you can make an Americano, which is similar to regular coffee with a richer body. Just follow this guide to making espresso with a semi-automatic machine and dilute the resulting cup of espresso with hot water.

References

1. Espresso Tamping. Retrieved July 10, 2019, from https://www.coffeeresearch.org/espresso/tamping.htm
2. How Does Pressure Affect Espresso Quality? (2018, June 21). Retrieved July 10, 2019, from https://perfectdailygrind.com/2017/06/how-does-pressure-affect-espresso-quality/
3. The Pump: The Heart of Your Espresso Machine. Retrieved July 10, 2019, from https://clivecoffee.com/blogs/learn/the-pump-the-heart-of-your-espresso-machine