Last Updated on October 20, 2021 by John Moretti
The bars of pressure that an espresso machine operates at are critical for the production of the espresso shot. The pressure that an espresso machine is able to achieve directly impacts the flavor of the espresso that the machine produces. This is why many find themselves wondering how many bars of pressure an espresso machine should use?
The latest research indicates that 9 bars of pressure is ideal for brewing espresso. Too much pressure will slow down the flow of water through the espresso, leading to under extraction. Too little pressure and the espresso will not extract at all. Some say that a varied pressure is the best option.
It is a fact that the pressure at which water flows through ground coffee beans is vital for the production of espresso. If you are buying an espresso machine, the pressure bars that the machine is capable of is an essential figure to look out for. Let’s take the time to better understand the optimum bars of pressure for an espresso machine.
How Many Bars Should An Espresso Machine Have?
The pressure that an espresso machine is able to achieve when brewing a shot of espresso is vital for producing the best shot of espresso possible.
Espresso machines require high pressure to force the water through the coffee beans allowing the shot to be brewed in a very short time. This is why espresso brews in about 30 seconds, while a French press may brew in 4 minutes.
The pressure that the machines operate directly determines the way the espresso tastes after it has been brewed. This means that the pressure that the machine operates at is vital, but how much pressure is best?
Research has found that the optimum fixed pressure for espresso brewing is 9 bars of pressure. At this pressure, the coffee is extracted well, it is extracted quickly, and the flow rate of the water through the ground coffee is not too slow or too fast, resulting in under or over-extracted coffee.
There have been years of espresso brewing research conducted, dating back more than 100 years now, when the first espresso machines were developed with steam pressure.
Since then, there have been advancements in espresso brewing, and it has since been determined that the ideal brewing pressure for espresso, with a fixed brewing pressure, is 9 bars; this equates t around 130psi.
Brewing at higher pressures can lead to serious coffee quality issues, and brewing at lower pressure produces an overall lackluster espresso brewing experience or no espresso brew at all.
How Many Bars Is Too Many?
Brewing at 9 bars of pressure is ideal for espresso, and brewing at pressures higher than this leads to some espresso quality issues.
9 bars of pressure is ideal because this pressure allows for water to be forced through the ground coffee, yielding the shot of espresso but not allowing the water to flow through the coffee grounds too quickly or too slowly.
If the flow rate is too high, the coffee will be under-extracted, leading to a sour cup.
If the flow rate through the coffee is too low, not all of the coffee with be reached by the water, which will also lead to under extraction, or the water will flow too slowly through the entire brew, which will lead to over-extraction of the beans, which results in an overly bitter shot of espresso.
If the pressure in the machine is too high, the water will compact the ground coffee as it flows, which will drastically decrease the flow rate through the coffee grounds.
This begins to happen at around 10 bars of pressure. This means that anything higher than 9 or 9.5 bars is too much for finely ground espresso coffee.
What Happens If The Pressure Is Too Low?
9 bars is ideal, and 10 bars is too much, but less than 9 bars can lead to its own set of problems as well.
I the pressure in the espresso machine is too low, the machine will not produce espresso. This will lead to long brew times and inconsistent coffee strength, which is more similar to drip coffee than espresso.
Low pressure can still be used to produce good espresso, but the brewing techniques are not the same as brewing espresso with 9 bars of pressure.
Brewing with less than 9 bars requires coarser ground coffee and longer brewing times. Anything less than around 4 bars of pressure can no longer be considered espresso.
More than 5 bars of pressure can produce good espresso, but the lower pressure threshold for excellent espresso lower than 9 bars is usually 6.5 bars of pressure.
Does The Pressure Really Make A Difference?
The pressure really does make a difference. Espresso has the flavor that it has and the iconic coffee intensity due to the pressure that it is brewed at.
Espresso is brewed very, very quickly compared to other brewing methods. This is why the coffee tastes the way it does.
Lower pressures require longer brew times, which may ruin the coffee, and change the flavor entirely. This takes the coffee way from espresso and closer to drip or pour-over coffee.
Brewing at high pressure allows for a high coffee extraction with very little liquid, yielding a very highly concentrated form of coffee, which we call espresso. This type of coffee is iconic and must be brewed in this way to be called true espresso.
This is the only way to brew espresso and to create the espresso-based drinks that we know and love, such as the Cappuccino and the Latté.
The Bottom Line
If you are in the market for purchasing an espresso machine, either commercial or for home use, it is very important that the machine is able to brew espresso at 9 bars of pressure.
This is a big ask for a home-use machine, in which case anything higher than 5 bars of pressure is acceptable with the right grind size and longer extraction times.
9 bars is critical for a commercial machine, as this will produce espresso at the standard that the modern coffee lover is accustomed to. Anything other than 9 bars, when using constant pressure, is simply not ideal for commercial espresso machines.
