Last Updated on
Yes, folks, today we’re here to talk about espresso machine BAR pressure and how it works…but before we get into BAR pressure, let us first begin with a quick definition for espresso, since it is needed to understand what BAR pressure is all about.
Espresso, contrary to what some people think, is actually a specific brewing method for preparing coffee, and this method depends on a certain amount of pressure as one of its requirements.
Sure, we all call it espresso and refer to it as a noun which describes a rich, creamy, caffeinated liquid brew, when it is more of a verb, or a process.
Consider this. Any kind of coffee bean can be used to make espresso, if you follow the rules of espresso preparation – but be aware that some beans taste better than others when put through the espresso-preparing process.
To clarify, coffee bags labeled as espresso are pre-ground coffee beans which are especially suited for brewing espresso, and usually its a blend of beans with different attributes that yields the best flavor for the final espresso brew. Lavazza espresso beans (pictured right) are a particular favorite for many espresso fans, and they are labeled as such (espresso beans).
Ok, so hopefully we’ve established something here with espresso, and now we can continue on to talk about BAR pressure in particular when it comes to espresso.
What Is Espresso Machine BAR Pressure?
As some of us know who have paid some attention to the espresso-making process (eg. watch a barista make it for you at your local coffee shop, or make it yourself at home), you will know that making espresso involves pushing hot water (almost boiling) through a compact ‘puck’ of grounds and a filter, at high pressure.
The water pressure is measured in “BAR” units. This “BAR” measurement, usually at around 9 BAR, when making espresso, is related to the Earth’s atmospheric pressure. So this 9 BAR measurement used for espresso coffee is approximately 9 times the atmospheric pressure or barometric pressure of the Earth at sea level. Say what? Yes, making espresso all ties in with the rhythms of the earth itself. No wonder the taste is so divine if its done right! Here’s a video which explains BAR pressure rather well, courtesy of the fine folks at Seattle Coffee Gear.
To return to our explanation of BAR measurement, we should be aware that the air in our atmosphere has actual weight. Because of gravity, this air weight is pushing down on the Earth’s surface. Similarly, the same pressure is used in the making of espresso coffee.
The amount of pressure or the number of BAR units of force, is very important to the flavors that are extracted from the coffee grounds.
Here’s a video with everyone’s favorite “Science Guy” Bill Nye, explaining “pressure” a bit further, as it pertains to atmospheric pressure (which, in turn, relates to BAR pressure for espresso).
Historically speaking, we can thank scientist Evangelista Torricelli in 1643, for inventing the first machine that measures this pressure. It is called a barometer and it measures pressure in bar units. No doubt you’ve heard of this device, as they are quite commonplace now, centuries later.
Here’s an illustration of Evangelista Torricelli below showing him using one of the first barometers.
As most baristas and espresso lovers know, there is a machine that is capable of producing the required BAR pressure for making a great cup of espresso coffee, and that is, of course, an espresso machine. These machines have become quite sophisticated over time and today we just want to focus in its ability to create this BAR pressure, mainly.
Espresso machines have many parts – they have, for instance, a group head, a portafilter, a boiler, and a steam wand. But what about that much-needed BAR pressure, which espresso machines use pressure to produce the dark, mysterious, rich, thick shot of coffee we call espresso?
Maybe your espresso machine is steam driven or piston driven. Piston driven is basically using a lever to create BAR pressure. Or maybe it’s pump driven. If you don’t like the manual machines, you can purchase an automatic espresso machine.
The thing is, not all espresso machines are capable of making espresso, which is something that might surprise some people. How can this be? Well, according to the SCAA (Specialty Coffee Association Of America), true espresso has a rather strict definition, and here it is:
Like we said before, we prefer to think of espresso as a process (brewing method / verb) more than a beverage (noun), but the point is that what espresso is not is a broad term which can be applied to anything from iced cream flavors, to anything which is brewed with beans that are called an “espresso blend”.
If you want to call any old thing espresso, feel free, but you will eventually offend those with delicate sensibilities (yes, the snobs).
Speaking of coffee snobbery, did you know that some people claim that a Moka pot can produce a tasty espresso by way of stove top brewing? Depending on who you ask, some will say that since Moka pots use pressure and steam to produce their brew, they are somewhat considered to be espresso makers as well.
Sadly, folks, just because the Bialetti is inexpensive, comes from Italy (home of espresso), and incorporates steam into its brewing method doesn’t mean you’re getting real espresso. To play the part of a coffee snob, we could simply quote the SCAA and ask, “Where are the 9 BARs of pressure that are necessary to make authentically?”
Sure, you might get some “espresso-style” coffee which is very dark and rich and perhaps delicious (which is fine with most of us coffee drinkers and even some espresso drinkers), but were you to claim that this was real espresso to a fan of true espresso, they’d probably slap your drink out of your hand, turn up their nose, and head back to Italy. Or maybe they’d just sip it, squint their eyes, and say “Espresso, you say? Really?”
To be fair, most people who have taken the time to educate themselves on a certain topic, or have an affinity for authenticity, whether it be with cars, food, books, film, and so on…those people (you can call them snobs if you want) usually take offense when someone presents them with what they consider a “fake” version of something, or an impostor of that thing they cherish so much. The same goes for espresso, and not-really-espresso.
So, yes, you do need that 9 BAR pressure to make real espresso. The way you create this pressure is essentially your choice. Ideally, 9 BARs are what you need. Too much pressure is unwarranted. The piston method delivers usually 8 to 10 BAR units of pressure, which in normal language, is 116 to 145 pounds per square inch (psi) of pressure. If all this sounds too complicated for you, Instead of using manual force, let the modern motor-driven pump provide the force necessary for espresso brewing. These particulars involving BAR pressure we’re discussing here are really what makes espresso espresso, and remember, not every machine that says it can make espresso actually can.
In 2005, the air-pump driven espresso machine emerged. These machines use compressed air to force the hot water through the coffee grounds. One of the advantages of the air-pump-driven machines is that they are much smaller and lighter than electric machines.
The first air-pump-driven machine was the AeroPress, which was invented by Alan Alder, an American inventor who also invented the Aerobie flying ring.
Soon after the Aeropress, which was a relatively recent invention, came the HandPresso Wild (which retails for about $100 on Amazon), invented by Nielsen Innovation (SARL), a French innovation House, and it was introduced in 2007.
More and more new ideas are hitting the market in order to help you with the perfect cup of espresso. Whether these devices produce a beverage that the SCAA would deem to be espresso is another thing, but we will admit that it is exciting to see so many new and interesting espresso-related gadgets hitting the market. Had Enough? We Didn’t Think So!
And so, we know, life is about balance and that is especially true in the world of coffee, and truer still for espresso. Now that we know that a certain amount of pressure is needed to call our drink espresso, what other insights are there to learn about this pressurized process that is espresso brewing?
To brew great cup of real espresso, a number of important things need to happen to allow human judgment to marry mechanical precision. It all begins in the kitchen, or, as the case may be – the garage.
Actually, where ever the bean roaster is located. Did you know you can now purchase yourself an excellent home roaster to roast your beans yourself? This is as close to the beginning of the home brewing process as you can get besides growing your own coffee plant (also possible).
At your local coffee shop, you will sometimes find a roasting machine that roasts the beans in house, which can be pretty interesting to witness although it can also be very loud. The guy or gal who does the roasting can also be called the the roaster (we kind of like ‘roast master’) will be making a blend of different coffee bean types to create a balance of flavors to end up with the most delicious elixer ever (if they know their craft, that is).
Will s/he use a particular bean to highlight a particular region in Africa? Maybe, but once these magic beans are in the hands of the expert who will prepare the drink, it is up to that person to make sure the beans are fresh, meaning no more than 2 weeks from the roast date.
The grinding must take place just before the brewing begins, as we mention time and again on this very website on our blog and also in our burr grinder review section – burr grinders being ultimately superior to the rest, with the Rocky to our right here being a prime example.
Some aromatics in ground coffee will evaporate within 20 minutes of grinding, so things must happen quickly but with precision.
The grind size will vary based on characteristics of the coffee such as age, bean variety, and the roast profile. Even at the highest level of espresso-making, there is no secret formula that is guaranteed every single time, but it helps to have a lot of hands-on experience before you get that sixth sense for what works. Regardless, if you are using an espresso machine, you will need to let it work its magic with the water, the temperature, the beans, and the BAR pressure …and of course time.
We said it before and we’ll say it again – 9 BAR is the standard pressure for making espresso. This standard has been reached through years of testing in the form of espresso drinking, and finally a standard was accepted by the Italian and American Coffee Associations and Guilds, not to mention World Champion Baristas. Do you think they are using Moka pots to make their world class espressos? Not a chance!
Professionals are always thinking about pressure, the kind of pumps, the flow rates, and more. Home machines use cheaper pumps and the pressure settings are pre-programmed for the homemaker. It might not be as precise but it should do the job.
It is important to keep in mind the correct combination of espresso machine BAR pressure, temperature, grind, and finishing color the works best with the beans you chose. Be prepared for the unexpected. Temperatures sometimes are difficult to control and pressures could stray from the norm. Burrs get dull and oils can build up in machines so that a good cleaning is necessary before you begin. If you want the taste and flavor to be to your preference, you must try really hard to control all the variables, because any wild-cards can damage or at the very least change the results.
A good barista can taste the espresso and know what changes need to be made for next time. If the BAR pressure is too high, the tastes will be weak and vice versa.
Temperature is also important. Proper espresso extraction occurs at 90°C to 96°C. Lower temperatures make the coffee to acidic and higher makes the coffee too bitter.
And finally, manipulating the color, volume, and time will also affect the end result.
You might get lucky and have an espresso machine that will do all the important stuff for you, but chances are you’re going to have to pay for it if you decide you want to become a master barista. There are alternatives, but they may not be the real deal. Keep that in mind.
Good luck and remember – BAR 9 is where it’s at!