What is the best bar pressure for a coffee machine (setting)?
Some people who ask us, “What is the best bar pressure for a coffee machine?” are prospective baristas who want to know what pressure setting they need to select at the group head to produce the best espresso.
Although baristas may have slightly different preferences, it is generally accepted that the answer lies somewhere in the 7 to 9 bar range.
Where does that come from?
The first person to suggest 8-9 bar as the ideal pressure was Desidero Pavoni, who bought the patent for the first espresso machine from its inventor Luigi Bezzera. He also recommended the ideal brewing temperature of 195ºF.
Unfortunately, achieving the ideal pressure was a challenge that Pavoni couldn’t overcome. His steam-driven espresso machines could only reach a maximum of two bar.
Eventually, Achille Gaggia, a Milanese cafe-owner, solved the problem with the addition of a cylinder containing a lever-operated spring-piston. For the first time, a barista could ‘pull a shot’ by forcing highly pressurised water through coffee grinds. The quick-thinking Gaggia also convinced his skeptical patrons that the foamy scum that started appearing on the surface of their drinks was actually due to his superior coffee that created its own creme. We now refer to this froth as crema, and understand that it’s the effect of air bubbles combining with coffee oils.
Since Gaggia’s lever-driven designs, we have been blessed with the electric pump. The best espresso machines will include a rotary pump that can pressurise water up to 15 bar and beyond. Vibratory pumps are a lower cost (and noisier) alternative that can also deliver highly pressurised water.
The next part of this article is for those people looking to buy an espresso machine and interested in the technical specifications.
What is the best bar pressure for a coffee machine (machine spec)?
You may be wondering: if 7 to 9 bar is the sweet spot for extracting a rich, tasty espresso, why even consider a coffee machine that advertises itself as 15 bar or higher?
There is no reason to discard such machines from your short-list, but it is important for you to dig a little deeper into the technical details of the machine. First, it is very unlikely that the machine will be set to apply a fixed 15 bar at the group head. This wouldn’t make any sense, because the machine would deliver espresso that is far too thick and over-extracted.
A machine advertising at less than 10 bar
For lower end espresso machines, the reality is likely to be that 15 or 18 bar of pressure is created at the pump, and that this reduces to around 9 bar at the group head. The marketing company may have used the higher number to win over the ‘higher is better’ brigade.
A machine advertising at more than 15 bar
A high end machine may actually be capable of creating 15 or more bar at the group head. This could cater for those baristas who like to start a shot off at 10 or 11 bar, before reducing to 9 to 10 bar. Such a machine is likely to include a feature for adjusting the group head pressure and also a pressure gauge.
So what do I need?
Ultimately, the devil is in the detail, and bar pressure is one of only a number of factors that should go into your final decision. Take a look at our range of commercial coffee machines, and please contact us if you need more specific technical information.