coffee-forum.net
Promoting coffee discussion.

Main
Date: 01 Sep 2007 11:19:01
From:
Subject: pressure FAQ
Single boiler, selonoid, no OPV:

Q. freshly roasted beans, finest grind+1, regular machine, 14-18 g.
fill, tamp: what's the expected brew pressure?

A. 8-10 bar.

Q. is it possible to brew a ristretto with 9 bar?

A. not possible.

Q. is it possible to brew a ristretto?

A. yes, at higher pressure.

Q. is it possible to choke?

A. with a good grinder: yes.

Q. is it possible to brew a 9 bar lungo?

A. not possible.

Q. does the temp influence the pressure

A. no (roughly)

Q: is the pressure constant during the shot?

A: not constant: end of the shot pressure is less due to deterioration
of coffee puck.

Single boiler, selonoid, OPV set to 9 bar

Q. ristretto at 9 bar?

A. possible.

Q. lungo at 9 bar?

A. not possible.

Double circuit HX with OPV:

Q. is the brew pressure any different from single circuit?

A. not at all

E61:

Q. anything special with respect to pressure?

A. nothing special

Lever machine with spring control of pressure:

Q: does it need an OPV?

A: yes and no.. A perfectly calibrated or adjusted spring could
theoretically provide an ideal pressure sequence during the shot
without OPV. More feeling required for the barista. Better chance for
different coffees (ristretto, lungo).





 
Date: 02 Sep 2007 16:44:56
From: Danny
Subject: Re: pressure FAQ
yuvali300@gmail.com wrote:
> Single boiler, selonoid, no OPV:
-snip weirdness-

What's all the rubbish about OPV, pressure and solenoids? As David
noted, original espresso machines (spring lever - as mine are) didn't
have or need the later additions, and are more than capable of
producing ristretto or lungo shots. It's *all* in the grind - you are
completely hung up on *pressure*.


--
Regards, Danny

http://www.gaggia-espresso.com (a purely hobby site)
(apparently bad grammar but I like it that way...)



 
Date: 01 Sep 2007 19:12:38
From: Barry Jarrett
Subject: Re: pressure FAQ
On Sat, 01 Sep 2007 11:19:01 -0700, yuvali300@gmail.com wrote:

>Single boiler, selonoid, OPV set to 9 bar
>
>Q. ristretto at 9 bar?
>
>A. possible.
>
>Q. lungo at 9 bar?
>
>A. not possible.
>

a lungo is certainly possible @ 9 bar.



  
Date: 02 Sep 2007 17:10:39
From: D. Ross
Subject: Re: pressure FAQ
Barry Jarrett <barry@rileys-coffee.com > wrote:



 
Date: 01 Sep 2007 19:53:03
From: lockjaw
Subject: Re: pressure FAQ
On Sep 1, 2:19 pm, yuvali...@gmail.com wrote:
> Single boiler, selonoid, no OPV:
>
> Q. freshly roasted beans, finest grind+1, regular machine, 14-18 g.
> fill, tamp: what's the expected brew pressure?
>
> A. 8-10 bar.
>
> Q. is it possible to brew a ristretto with 9 bar?
>
> A. not possible.
>
> Q. is it possible to brew a ristretto?
>
> A. yes, at higher pressure.
>
> Q. is it possible to choke?
>
> A. with a good grinder: yes.
>
> Q. is it possible to brew a 9 bar lungo?
>
> A. not possible.
>
> Q. does the temp influence the pressure
>
> A. no (roughly)
>
> Q: is the pressure constant during the shot?
>
> A: not constant: end of the shot pressure is less due to deterioration
> of coffee puck.
>
> Single boiler, selonoid, OPV set to 9 bar
>
> Q. ristretto at 9 bar?
>
> A. possible.
>
> Q. lungo at 9 bar?
>
> A. not possible.
>
> Double circuit HX with OPV:
>
> Q. is the brew pressure any different from single circuit?
>
> A. not at all
>
> E61:
>
> Q. anything special with respect to pressure?
>
> A. nothing special
>
> Lever machine with spring control of pressure:
>
> Q: does it need an OPV?
>
> A: yes and no.. A perfectly calibrated or adjusted spring could
> theoretically provide an ideal pressure sequence during the shot
> without OPV. More feeling required for the barista. Better chance for
> different coffees (ristretto, lungo).

who are you talking to?