How Do Espresso Machines Work? : Don’t Buy Until You Read This

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How Espresso Machines Work

By Melanie Rose

It wasn’t that long ago that I bought my first espresso maker — a small semi-automatic that was a good machine in it’s price range, but not the best espresso machine to be had. I made the decision to craft my own espresso at home due to the fact that I was spending anywhere from $8 to $20 a day at local cafés. I would haul in my trusty laptop and camp for the better part of a day while savoring ambient conversation, sipping rich espresso and taste-testing scrumptious pastries. Between my pocketbook and my waistline it’s hard to say which was suffering the most.

I do have great fondness for a good coffee house. The place I will always love the most usually has the front and back doors open and brave pigeons waddle in to pick crumbs from the floor. The fragrance of brewing coffee and baking delectables permeate the air, mixing with the sounds of people coming and going. Ahhhhh, so sweet. Once or twice a week I still visit the local coffee house and relax or do some work so that I can sunbathe in the warmth and glow of a great café.

But whether you partake at home or at the local café, espresso has a way of pulling you into its rich world. It wasn’t long after buying that first little machine that I was grinding my own beans and experimenting with different blends of coffee. I began conducting all types of research on how to illicit the flawless shot from a machine with understandable limitations.

Along the way I’ve learned a lot, but creating a great shot of espresso is like living the Tao. Elusive, slippery, and an ongoing process. It’s an art form that you can play with for a lifetime, and I guess that appeals to me.

In my search for espresso perfection I’ve run across so much terminology that I found confusing, so I wanted to share what I’ve learned about how espresso machines work, what all that lingo means, and why it’s important if you are a true seeker as I am.

I’ve included some diagrams so that you can have a visual, too. These are very basic because there is so much variation between machines and manufacturers, but they give you a general idea of the workings of an espresso machine.

First Things First

Before I get into describing the inner workings of the machine, I want to run through the process of extracting (aka pulling) a shot. The term “pulling” comes from the old time baristas using their lever machines.

Essentially, the shot is produced by propelling between 1 and 2 ounces of hot, pressurized water through a firm bed of finely ground espresso coffee.

In order to extract the shot from your espresso machine, the first thing you need to do is to check the reservoir tank and make sure that it’s full. Some of the pricier espresso machines can be plumbed into the home, in which case this step won’t be necessary.

Next, you place the ground espresso into the portafilter and tamp it down in order to produce a tightly packed bed of coffee. The portafilter is attached to the machine by twisting it into a unit that contains the gouphead, a component which attempts to evenly distribute the water onto the coffee. The portafilter sits just below the grouphead.

Now you will turn on the machine and let it heat up. The time this takes varies depending on the machine, but 10 to 15 minutes is about average. A light on the control panel will indicate when the water is at the ideal temperature of around 250?F, just below boiling point. Most espresso machines have a cup warmer on the top of the machine, and you should not only heat your cup there, but place some boiling water in it and then toss it out right before extracting the espresso so that the cup is almost hot.

espresso machine infographic

© 2013: Coffee and Juicers

When you’re ready, you will place the cup on the drip tray beneath the portafilter and extract the shot. Depending on what type of machine you have, you will perform different activities in order to do this. With super-automatic espresso machines you will simply push a button. With a semi-automatic there will be more you’ll need to do. But ideally you will extract just under 2 ounces of syrupy liquid espresso and it will take 30 seconds to a minute. A good shot will have a foamy, creamy head, appropriately called the “crema”, which is Italian for “cream”.

We’re just covering the basics here, but as you learn more, you’ll start paying close attention to the freshness and grind of the coffee, the water temperature and pressure, and how tightly you pack the coffee with the tamper. All of these factors need to be considered in order to extract a fine shot of espresso.

Steaming and Frothing Milk

The best espresso machines will have a wand for steaming and frothing milk, also called a panarello. You use this when you want to make a latte, cappuccino or macchiato. As a side note here, I’ve used coconut milk as well as almond and hazelnut milk, and they work almost as well as whole milk for these espresso drinks.

A lot of people like to have a separate container, or frothing pitcher for this purpose. You can also just froth the milk in a separate mug or cup and then pour it over the espresso. Skilled baristas like the frothing pitchers because the pouring spout allows them to make espresso “art” as seen in this photo.

latte art

photo credit: javajoba on flickr

To make a latte, you would submerge the wand into the milk and turn a steaming valve switch on. The switch will reactivate the heating element, which rapidly re-heats the water in the boiler. Steam will emit from the wand and will quickly heat the milk. Placing the wand’s nozzle close to the surface of the milk should deliver a nice froth for cappuccino or macchiato espresso drinks.

Inside the Machine

The Control Panel

Most machines these days have a lit control panel, with the exception of the lever espresso machines, which are mostly hand operated. At the very least, the control panel will have an on/off light and a temperature light that indicates when the water is sufficiently hot to extract the shot of espresso. It will also have a valve for controlling the flow of steam into the steaming/frothing wand. The higher end machines generally have more lights and indicators that help you to gauge the pressure and temperature more precisely for pulling quality shots of espresso.

espresso machine infographic

© 2013: Coffee and Juicers

The Reservoir

All espresso machines need to have a water delivery system. This is called the reservoir. On lower end machines, the reservoir is a container that is removable from the machine that you fill up with water by hand. Commercial espresso machines and some of the higher end individual espresso machines are equipped to be plumbed into your home’s water system. The water in the reservoir is cool or room temperature. Heat and pressure are applied once the water leaves the reservoir and is pulled into the pump and the boiler.

The Pump

The pump draws water out of the reservoir and pumps it into the heating chamber at high pressure. The desired pressure is 9 – 15 bars. A bar is simply a measurable unit of pressure equivalent to 100,000 newtons per square meter or approximately one atmosphere. An atmosphere is a unit of pressure equal to mean atmospheric pressure at sea level. This was very confusing to me when I went shopping for my first espresso machine. I thought that bars were literally rods of metal in the machine that somehow made the espresso taste better! I’m clearly no physics intellect.

The Boiler

The boiler is crucial because this is where the heating of the pressurized water is conducted. The boiler is a metal chamber that has a heating element built into the bottom of it. The heating element is a spiraling filament that heats up when electricity is applied to it. Often the heating element is embedded in plaster or other materials in order to increase it’s durability. The boiler has a one-way valve that lets water into it’s compartment from the pump, but it won’t let the water go back into the pump. Instead, the water then travels to the grouphead.

I should mention that the more pressure, or bars, that is applied, the higher the boiling point of the water. Water at sea level pressure (or one bar) boils at 212?F. By the time that you have reached around 9 bars — widely accepted as the proper amount of pressure for espresso brewing — the boiling point is right around 250?F.

The Grouphead

© 2013: Coffee and Juicers

The grouphead is the component that delivers the hot, pressurized water to the bed of coffee that lies waiting in the portafilter. In the diagram, you can see that the portafilter unit is solidly fit into the element that contains the grouphead. There are many tiny holes within the grouphead for the purpose of creating an even, cross-sectional flow of water onto the ground coffee. All traditional espresso machines have a grouphead, and commercial machines often have more than one.


The Portafilter

© 2013: Coffee and Juicers

The portafilter is the removable part of the machine that holds the ground coffee. It consists of a handle, a body, a basket and a two-pronged spout. Inside the portafilter’s basket is where the ground coffee is tamped and packed. The portafilter is then fastened to the grouphead component in order to form a seal. Below the basket are the two spouts from which the espresso actually emerges and flows into your warm cup.


In Conclusion

I sincerely hope that this article has helped to clear up any confusion you might have had about espresso machines and how they work. If you are trying to decide whether or not to buy your own individual espresso machine, this information can shed some light so that you have an idea of what you are looking for as you browse.


Hi, I’m Melanie Rose,  president of Coffee & Juicers. I love espresso, and I love juicing, so I provide in-depth, honest, online reviews of the best espresso machines and the best juicing machines out there. Hundreds of websites promise to give honest reviews for these appliances, but in fact they are not usually well researched or relevant to your needs. Coffee and Juicers provides you with complete and unbiased reviews so that you can have a less time-consuming and more satisfying shopping experience.

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