The pressure of consistency

[Shotgun Senior Member Find all posts View Profile Close Shotgun]

Hi all,
Ive had my serious espresso machine (Vibiemme Domobar Super) for just over 6 months now and thanks largely to the assistance Ive received here, Im pretty happy with what Im drinking.

Im sure Im not Robinson Crusoe here but consistent shots and consistent flavour is my greatest challenge. The other day I was nosing around the home-barista.com site and fpound the following quote relating to an owner of the same espresso machine.

My brew pressure was running a little on the high side, over 10 bar. I pulled the covers off this evening and made a small pressure change. It is just under 9 bar now. When you change one variable, you have to compensate by changing several others. Reducing the brew pressure required a revisit on the grind and dose settings.

Previously, I was having extraction issues with the higher pressure. I had to grind much finer than normal and was dosing up. I was getting uneven extractions and pitting (channeling) on the puck. I have also changed coffee, which is another major variable change. Right now I am feeding the Super some Black Cat from Intelligentsia Coffee Roasters. I have lowered my dose and coarsened up the grind. With Black Cat, I am dosing 15 grams in the stock double basket and hitting the sweet spot.

Now, when I pull shots, my pressure gauge (on the top right) tells me that the pressure is around 11 bar. See photo during extraction below.

My question is, could the high pressure be having an adverse effect on my consistency as indicated by the post on home-barista.com? Is it that relevant and where do all you knowledgeable folk believe it should be?

Thanks all,
Tony

[A_M Guest Find all posts View Profile Close A_M]

Re: The pressure of consistency

Hi all,
Ive had my serious espresso machine (Vibiemme Domobar Super) for just over 6 months now and thanks largely to the assistance Ive received here, Im pretty happy with what Im drinking.

Im sure Im not Robinson Crusoe here but consistent shots and consistent flavour is my greatest challenge. The other day I was nosing around the home-barista.com site and fpound the following quote relating to an owner of the same espresso machine.


Now, when I pull shots, my pressure gauge (on the top right) tells me that the pressure is around 11 bar. See photo during extraction below.

My question is, could the high pressure be having an adverse effect on my consistency as indicated by the post on home-barista.com? Is it that relevant and where do all you knowledgeable folk believe it should be?

Thanks all,
Tony

YES and NO..  

There are many assumptions and the first that needs to be validated is the actual pressure at the group..

Gregs pressure gauge would be a good start.

From there I think any number of the points raised on the other forum is relevant.  Every action has an  = and opposite reaction.

Change ya pressure ( temp)  then grind and tamp and dosing will need to be re visited.  In essence the lower the pressure the more impact would be seen when changing Beans / grind / tamp and dose etc... But like always; there are windows  of settings and a change in pressure has other  impacts etc. And when playing on the edge.. A slight change in one can have an significant change in another.

I know that some systems are often set to about 1.1 bar and that makes it a bit easer for some (new users) when playing with dose / grind and tamp..

Trust that helps to set the context...

But first things first... Confirm Pressure and temp at the head.... That then is ya benchmark.

[beanflying Senior Member Find all posts View Profile Close beanflying]

Re: The pressure of consistency

Also the pressure gauges on machines tend to read a bit high (varies from machine to machine) Actual pressure at the puck may be about 1 bar or so lower.

[barri Senior Member Find all posts View Profile Close barri]

Re: The pressure of consistency

All the material Ive read on a VBM (super or junior) indicates that the brew pressure should be between 9 and 10. Mine is nearly always about 10 so I think your setting seems high.