What is a bar?

[Tex]

Well, I'm not talking about the place your friends took you to get over ol' what's her name. I'm talking about that mysterious pump bar rating you see in the home espresso machine ads.

1 bar = 14.5 psi

When a machine is said to be capable of 15 bar,  it's capable of producing 218 psi. Since CW holds that espresso is best made using 9 bar (131 psi), you can see why some consider the pump rating as meaningless. What's important is whether the pressure can be regulated so the pressure used for brewing is at the proper level as the water hits the coffee. That's where an adjustable pressure relief valve (or OPV) comes in. The OPV lets you reduce the pressure in the group (using a gauge) to the proper level.

Pressure is just one variable that must be controlled in order to produce quality espresso. I'll go into the other variables at another time

Enjoy!

[mp]

Thank you for that fine explanation of "bar" Robert.

 

[Tex]

Thank you for that fine explanation of "bar" Robert.

 

I thought that called for a drink, so I went to my favorite, low-pressure bar.

 

[J.Jirehs Roaster]

Well, I'm not talking about the place your friends took you to get over ol' what's her name. I'm talking about that mysterious pump bar rating you see in the home espresso machine ads.

1 bar = 14.5 psi

When a machine is said to be capable of 15 bar,  it's capable of producing 218 psi. Since CW holds that espresso is best made using 9 bar (131 psi), you can see why some consider the pump rating as meaningless. What's important is whether the pressure can be regulated so the pressure used for brewing is at the proper level as the water hits the coffee. That's where an adjustable pressure relief valve (or OPV) comes in. The OPV lets you reduce the pressure in the group (using a gauge) to the proper level.

Pressure is just one variable that must be controlled in order to produce quality espresso. I'll go into the other variables at another time

Enjoy!

So is this a trick question or a rhetorical question??

[peter]

So is this a trick question or a rhetorical question??

So is your question a trick question or a rhetorical question??  

[mattquist]

For those whom are truely anal (and there must be some of that here), here's a link to convert bars to psi, or the ever popular pascals.  If your beyond anal, then you can even take it out to the sixth decimal.

http://www.lenntech.com/unit-conversion-calculator/pressure.htm

[headchange4u]

Bar is also a measure of atmospheric pressure.

[mp]

Ok ... everybody is right ... can we assume that being a coffee forum that bar in this mention is about the pressure you need from your espresso machine in order to produce an excellent cup of espresso?

I am just asking?

 

[nilesong]

Nice explanation, thank you!

[J.Jirehs Roaster]

Ok ... everybody is right ... can we assume that being a coffee forum that bar in this mention is about the pressure you need from your espresso machine in order to produce an excellent cup of espresso?

I am just asking?

 

I believe that in Europe 'bar' is the common unit of measure for pressure..
most of the espresso tradition comes from Europe so bar would be the scale on the gauges...
I experienced the same issue when I was playing with 3000 psi air rifles... all the European shooters talked 'bar' in the tech forums

so look out Tex... the metric system is sneaking in on you 

[milowebailey]

... this whole time I though Bar was what was raised when I started homeroasting.....


Milowebailey definition of bar-

a dynamic ratcheting standard by which the quality of a cup of coffee expected, is measured

[ButtWhiskers]

Since CW holds that espresso is best made using 9 bar (131 psi),

Well CW is a n00b.    

9.6 bar (~140 psi) works much better in most instances unless you are using burnt, oily, overroasted beans.

[Tex]

Since CW holds that espresso is best made using 9 bar (131 psi),

Well CW is a n00b.    

9.6 bar (~140 psi) works much better in most instances unless you are using burnt, oily, overroasted beans.

I've found 8.5(ish) seems to produce more crema and less-bitter tastes in the lighter roasts I prefer (FC+ max). Guess that's why this is considered more art than science: Vive la différence!

[Tex]

Ok ... everybody is right ... can we assume that being a coffee forum that bar in this mention is about the pressure you need from your espresso machine in order to produce an excellent cup of espresso?

I am just asking?

 

I believe that in Europe 'bar' is the common unit of measure for pressure..
most of the espresso tradition comes from Europe so bar would be the scale on the gauges...
I experienced the same issue when I was playing with 3000 psi air rifles... all the European shooters talked 'bar' in the tech forums

so look out Tex... the metric system is sneaking in on you 

Actually bar isn't an officially internationally recognized symbol (SI units or cgs units). But it is accepted in both categories because of its wide spread use. Guess you could look at it as the bastard son that was successful?

[Tex]

... this whole time I though Bar was what was raised when I started homeroasting.....


Milowebailey definition of bar-

a dynamic ratcheting standard by which the quality of a cup of coffee expected, is measured

Has anyone actually tasted the dudes coffee? Ratcheting up the bar is a relative term - he may be doing the low-bar limbo.