November 13, 2006

What does "15-Bar or 19-Bar Pump Driven Espresso Machine" mean?


I have been getting a lot of people writing in asking about what does 10-bar, 15-bar or 19-bar pump driven mean when we talk about espresso machines. First to start out, a "bar" is a scientific term for pressure. It's about equal to an atmosphere of pressure, or about the ambient pressure at sea level (all approximate; we're not in science class here). So, a 15-bar pump will deliver about 15 times the pressure at sea level; it's fairly high pressure. So, when you see 15-bar pump-driven espresso machine, in the description, you should take away that this machine pumps the hot water through the ground espresso at high pressure.

Why is it important to have a Pump Driven Espresso Machine?
There are a couple of kinds of espresso makers out there: Steam driven and Pump driven (there's also manual where you are the pump). Steam driven machines are less expensive, and when the water boils, it develops only 2-3 bars of pressure to push the hot water through the espresso. In order to get the foamy crema on top of an espresso, which is emulsified oil and air, you need the higher pressure of a pump driven espresso machine. So, if you want better tasting, crema topped espresso, go for the pump-driven espresso machines.

Is 19-bar better than 15-bar?
Not necessarily. A lot has to do with how the machine is constructed, and how much of that pressure actually gets applied to the coffee grounds; it could be that a lot of pressure is lost in process, and doesn't actually get to the coffee grounds.

We have reviewed a lot of inexpensive pump driven espresso machines as well as some more expensive ones - check out our reviews in our Espresso Machine archive.

Read More in: Espresso Basics

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Posted by Scott Martin at November 13, 2006 9:44 AM
Recent Comments

That's not actually correct. The optimal pressure for extracting espresso is 9 bar. Most vibratory pumps have a maximum output of 15 - 17 bar, however this does not mean to say that this is the right pressure to brew espresso under. For this reason most good machines will have a pressure release valve (aka OPV - over pressure valve) to reduce the group pressure by diverting excess flow back into the water reservoir. Machines like the Gaggia Classic have an adjustable OPV and therefore you can calibrate the machine to brew at exactly 9 bar via some methods (google "Gaggia OPV mod" if you're interested). If the pressure is too high - ie in the range of 12-17 bar - then it will be very difficult to brew good espresso and the margins for error with tamp and grind will be very small.


Posted by: Luciano at September 3, 2010 5:37 PM

The 15-bar pressure is the optimal "pressure" to to get all the essences of coffee. As you know, the espresso machines works on the method infusion, injecting pressurized hot water into coffee blend, with the force of 15-bar.
Some start level (basic, low cost) espresso machines, works with less power than 15-bar.


Posted by: Josepe at November 26, 2009 6:16 PM
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