If you’ve been looking to buy an espresso machine, you have most likely heard of BAR pressure at some point. Manufacturers of espresso makers usually mention BAR pressure on the box as it is an important variable to consider while shopping for one.
Unfortunately, the description on the box doesn’t go further than something like “15 bar” most of the time, creating room for a lot of confusion as to what BAR pressure actually means.
So what really is BAR pressure? Let’s find out.
Why Is BAR Pressure Important?
To understand what BAR pressure is, we must first take a look at how an espresso machine functions, and why pressure is a major deciding factor when it comes to purchasing one.
As you know, brewing espresso requires pressure to force the hot water through coffee grounds. When water is pushed through the grounds with such pressure, the extraction process takes place where the flavors of the coffee grounds are transmitted to the water. The amount of pressure plays an important role when it comes to the extraction level of the espresso, which directly impacts your coffee experience.
While under-extraction will cause your espresso to turn out sour and weak due to some components of the coffee staying undissolved, over-extraction will leave you with a very bitter cup of coffee as the bitter components of the grounds which shouldn’t have been extracted will make their way into your drink. For this reason, your espresso maker must use the ideal amount of pressure to achieve a balanced level of coffee extraction.
A balanced level of extraction will produce an espresso that contains the full flavor profile of coffee grounds without extracting the unwanted chemicals, ensuring that your cup of coffee turns out perfectly.
What Really Is BAR Pressure?
Simply put, BAR is actually a unit for measuring pressure. When you see an espresso machine mention something in the lines of “9 bar”, it refers to the maximum amount of pressure the machine can exert.
The maximum pressure being 9 bar doesn’t necessarily mean that the water pressure by the time it hits the coffee grounds will also be 9 bar, as the way a vibratory pump operates (which are found most commonly in domestic espresso makers) creates inconsistencies and pressure loss along the way.
Now we know what BAR actually is, but this information by itself still doesn’t really help us understand whether the amount of pressure is ideal or not. To put all the pieces together, we need to know the ideal pressure to look for in an espresso maker.
What Is the Best BAR Pressure for a Coffee Machine?
Between 7 and 9 bars of pressure is usually considered to be the best amount. Please note that this range refers to the pressure of water at the time it comes into contact with coffee grounds, and not the maximum pressure an espresso machine can provide. If you’re wondering why these figures are considered to be optimal, the answer is simply trial and error.
Over years of espresso brewing and optimization, brewers eventually found out that this range of pressure yields the best results for the most part. While there is always room for micro-optimizations as the optimal pressure depends on factors such as grind size, between 7 and 9 bars are considered to be a good ballpark figure where further optimization doesn’t really change much.
Espresso makers are often pre-configured in a way to ensure that the water pressure falls in this range without any need to manually adjust the pressure setting.
What Happens if Pressure Is Too High or Too Low?
Since between 7 and 9 bars of water pressure is optimal, we can consider anything below 7 bar to be too low and anything over 9 bar to be too high.
Not staying within the optimal pressure range will negatively affect our espresso, causing under-extraction, or over-extraction.
With a quality espresso machine,’ you will most likely never have to worry about this, as the machine will ensure that optimal pressure is used to brew your coffee.
Why Do Coffee Machines Have More Pressure Than Required?
We have been talking a lot about how between 7 and 9 bars of pressure is optimal, yet a lot of coffee machines come with bar pressures all the way up to 20 bar, which could be confusing.
Realistically, you will never need a 20 bar espresso machine as these machines never use the maximum amount of pressure they are capable of for the reasons we have been talking about. Most of the time these high figures are used as a marketing gimmick, making people believe that more bars are better.
Even though the pump is capable of generating 20 bars of pressure, the pressure of water that hits the coffee grounds is actually depressurized to the optimal range of 7 to 9 bars, meaning that you’re being charged for something that you’ll never be using.
That being said, you’ll find a lot of reasonably priced espresso makers having 12-15 bars of pressure instead of the 9 bars we have been talking about. As the pump pressure and the pressure of water when it hits the portafilter is often not equal due to pressure loss caused by how the pump operates, having a few extra bars of maximum pressure ensures that the machine can constantly exert the optimal amount of pressure.
How Do Coffee Machines Generate Pressure?
In every espresso machine, there is an electric pump that is responsible for generating pressure. These pumps separate into two categories which are rotary pumps, and vibratory pumps.
Vibratory pumps are most commonly found in espresso makers we use at home. These pumps are known for being inexpensive and small, which is the reason most home espresso makers employ vibratory pumps instead of rotary pumps.
As vibratory pumps are piston operated, there are times where the water pressure is inconsistent due to piston movement not being constant, creating a loss of pressure over time. This is the main reason for home espresso machines having higher maximum pressure than what is actually needed, allowing them to compensate for the loss.
Rotary pumps are more advanced than vibratory pumps, which is why they are mostly found in professional-grade espresso machines. They are larger and more expensive than vibratory pumps, but they also provide a better experience.
These pumps utilize a spinning disc to create pressure, and since the movement of the disc is uniform, there is no inconsistency or loss in the pressure exerted. While these pumps are also often capable of exerting a greater amount of pressure than required, they are configured to provide the optimal amount of pressure needed.
The amount of pressure an espresso machine can exert is definitely an important thing to consider when you’re looking to buy one as your drink can easily be ruined if the coffee grounds aren’t extracted optimally.
We hope that we managed to help you understand how pressure actually affects your drink so that you don’t fall for the marketing strategies which are designed to make you spend more money without getting any benefit out of it.
Have a great day and enjoy your coffee!