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Date: 29 Mar 2007 14:49:49
From: gscace
Subject: Pressure Profiling Update 3
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Pressure Profiling Update 3
I think I'm homing in on some concrete information about pressure
profiling that is worth blabbing on about, so here goes:
First thing is that there seems to be a practical maximum pressure
value beyond which things go to hell in a handbasket tastebudswise. I
found this out when I was experimenting with pressure profiles that
included a high-pressure hump at the beginning of the extraction.
Values for the hump were as high as 165 psi (11.3 bar). My thinking
was that if sweetness was extracted early in the brewing process, then
maybe I could emphasize it by increasing pressure to a high value
early on, reducing to more conventional values later. The result was
that I extracted crema that was kedly bitter. Bitterness was muted
by reducing the magnitude of the hump. Bitterness was removed once
the max pressure value was reduced to 9.5 bars at the coffee cake,
which adds credence to the conventional 9-bar wisdom. I learned later
that Jim Schulman has also observed this effect. I also successfully
replicated the effect for Peter Lynagh, of Terroir Coffee, when he
came down to visit.
Once I learned that there was a maximum practical brewing pressure, I
began to think of pressure profiling in terms of the minimization of
undesirable tastes, rather than in terms of super-extracting desired
compounds. Taste tests with Nick Cho demonstrated to me that the
sweet tastes and mouthfeel are developed early in the brew process,
with dilution occurring later. Unfortunately, in the tests mit Cho
(gesundheit!) extraction of bitter compounds also occurred during the
dilution phase, meaning that a balance needed to be struck between
dilution of the drink to a desired volume and introduction of negative
taste components. Reducing the brewing pressure as brewing progresses
seems to be beneficial in reducing bitter tastes extracted during the
dilution phase. Tests with Nick pointed to accentuated sweetness in
Counter Culture Toscana, which in retrospect was really a subtraction
of bitter components added in the last third of the brew process.
The most successful general profile that I have come up with to date
(I've now got an excel file with a bazillion profiles mapped out in
it) is a pressure profile in which the pressure rapidly increases from
some nominal start value to 9 bars at the group (elapsed time of 1
second from start to full pressure) with a short 9 bar soak, then
ramps downward in a slow linear fashion (straight line degradation) to
around 7 =BD bar, with a more rapid, second-order (curved downward)
slope over the last few seconds to around 6 bar, arriving at 6 bar 30
seconds after initiation of the brew cycle. This general shape can be
used with or without a pre-infusion step. The pre-infusion that I've
been using is to soak the cake at around 2 - 3 bar for 3 seconds, then
quickly ramping to maximum value with an exponentially increasing
slope. Full pressure is attained 3 seconds after the end of the low-
pressure soak. This combination produces liquid evenly over the
bottom of the filter basket almost as soon as the pressure begins its
rapid increase. Regardless of whether or not pre-infusion is used,
I've been using a very similar profile toward the end of the brewing
period. If pre-infusion is not used, I increase the time of the high-
pressure soak by a few seconds.
It seems to me that the efficacy of preinfusion is coffee specific.
There are three basic coffees that I've inflicted pressure profiling
upon and with which I can comment. I've been drinking dry-processed
Ethiopian SOs, and Ethiopian-based simple blends that have a lot of
mouthfeel and body. My tests with Nick used Counterculture Toscano.
I don't really know what is in it, and for the purposes of this
discussion I don't think I really need to know. And last weekend,
Peter Lynagh and I concentrated on a very lightly roasted Brazil.
Here's a link to Terroir's information about the coffee:
http://info.terroircoffee.com/content/view/17/2/
For brewing temps, the Ethipian DP and Toscano seem to like around
201F. The SO Brazil was brewed at 195 F. The blends seem at first
blush to benefit from preinfusion. I think that the soak and
subsequent rapid pressure ramp may produce more mouthfeel, but I need
to revisit this as I haven't been systematic enough, particularly in
light of our results with the Brazil. We found that pre-infusion was a
waste of extraction time when brewing the SO Brazil. Unlike the
blends, the SO Brazil produced two predominate tastes with great
clarity - nuts and sweetness reminiscent of dried figs. Both
nuttiness and sweetness were enhanced when the pre-infusion step was
removed. The clarity of the Brazil made differences between brewing
at constant pressure and brewing with profiled pressure easy to
discern. Bitter tastes were evident with constant-pressure brewing
and demonstrably removed by profiling.
Recently folks have come up to me on the street, shoving their pudgy
fingers in my puny chest, demanding to know that if pressure profiling
meant deemphasizing the last portion of the brewing process, why not
just stop brewing early? After I imagine breaking their finger with a
deft ital arts-type motion, I counter with the argument that early
brew termination is different. Compare two shots of the same volume,
but with one brewed in the style of brewtus interruptus, and the other
brewed to satisfying completion with pressure profiling. If one
terminates early, for example at 18 secs in a 27 sec extraction, the
volumetric flow rate during the 18 second period is much faster than
the flow rate for an extraction taking place over the entire period.
The extractions that we are observing with profiled pressure have more
or less constant flow rate throughout the entire time period, which
means that the volumetric flow rate is less by 50%, but over a longer
time period. This changes the taste.
As I try different coffees and gain more experience I'm getting more
confident that pressure is worth exploring as a brew parameter. There
is still a lot to learn here, but the tests with Terroir indicate that
variable pressure is useful when one is brewing clean SO espressos in
which one or two tastes are showcased. I'm not sure which cart drives
which horse when it comes to blends. I don't know if various widely
used pre-infusion schemes were developed because they work with
traditional blends, or if blends end up being developed to mask
machine deficiencies. My cynical self thinks it's the latter. I have
a lot more to learn about this, and it gets more difficult when I'm
using coffees I've munged together. I don't feel like I'm a good
enough roaster or blending dude to come up with confident conclusions,
other than to go back with what I learned about the Brazil SO and see
if I can make any hay with the stuff I usually drink. That means I'm
not close to closure, which means that if you all don't behave, rather
than dislocate your digits I'll spring Pressure Profiling Update 4 on
you.
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Date: 30 Mar 2007 12:25:06
From: gscace
Subject: Re: Pressure Profiling Update 3
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On 30, 12:56 pm, "DavidMLewis" <DavidMLe...@mac.com > wrote:
> On 29, 6:26 pm, "gscace" <gregory.sc...@nist.gov> wrote:> Oh, yeah. One other thing that I want to try is to use a shallower
> > basket than the LM ridgeless double, maybe like the Faema double
> > basket, but with steeper walls. I'm thinking that the shallow cake
> > with full 58mm width might promote clarity over deeper baskets since
> > the radial temperature gradient in the cake will be less during the
> > early phases of brewing. Barry and I talked about building a variable
> > depth basket for just these sorts of shenanigans.
>
> Hi Greg,
>
> Very impressive. I don't think I understand, though, the difference
> between the baskets that you're referring to here. Is it that if you
> down-dose the LM basket, say with a curved scraper, you have
> relatively more of the cake in the curved portion at the bottom?
>
> By the way, a confounding factor in the Swift baskets is that the
> holes are larger, or at least that's my understanding from the dealer.
>
> Best,
> David
I thought it might be a whole lot easier to dose a basket whose
internal volume was close to what I was looking for. My pump system
runs like crazy if it is trying to fill a big void,such as in filling
a down-dosed triple basket. It quickly fills the airspace with water
and then pressurizes the system according to the profiling program.
If the headspace is less, the pump responds differently according to
the different geometry, but providing the same pressure ramping rate.
I dont' yet know the effect of headspace on brewing after the pressure
rise, but I think the pressure transducer and feedback control more or
less remove different headspace volume as a variable in the pre-
infusion / pressure rampup process.
WRT hole size, the baskets themselves do not provide much pressure
resistance. I'd expect hole size in baskets to have little effect.
The diameter of a critical flow nozzle for the volumetric flow rates
and pressures that we are considering is 0.013 inches. The combined
cross-sectional area of all of the holes in a basket is a lot larger
the cross sectional area of the critical nozzle.
-Greg
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Date: 30 Mar 2007 12:16:15
From: gscace
Subject: Re: Pressure Profiling Update 3
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On 30, 1:44 pm, jim schulman <jim_schul...@ameritech.net > wrote:
> On Fri, 30 2007 11:34:31 -0400, "Jack Denver"
>
> <nunuv...@netscape.net> wrote:
> >I'm still not picturing what your "double" dispersion block looks
> >like (picture is worth 1000 words).
> >http://i12.photobucket.com/albums/a240/jim_schulman/Elektra/MicroCasa...
>
> part 22 is the actual dispersion block, but the group bell, 20, has
> it's own set of holes. Part 22 might fit into other groups.
>
> Although Greg reports better results with the shallow Rancilio basket
> when low dosing (the NS double basket is similar), I think that if
> there's problems with water dispersion and pressure, going to a triple
> basket may help, since this gives extra headspace and more of a
> preinfusion. Here's a graph of dwell time versus dose using a triple
>
> >http://www.home-barista.com/forums/userpix/18_dose_versus_dwell_1.gif
>
> The counterargument is that the headspace becomes filled with brewed
> coffee, and that this fraction of the puck is lost to the cup.
>
> Petracco, in Illy and other papers, says the puck behaves very
> "non-linearly" early in the shot as the fines settles and the grind
> particles soak, swell, and interlock into an aggregate. This probably
> implies that the fine structure of the puck may depend sensitively on
> all sorts of little things that happen before one sees the first drop.
It might be that I'm getting this result because the pump output is
pressure controlled and the pressure ramps in a more orderly way than
an unregulated pump.
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Date: 30 Mar 2007 11:04:00
From: DavidMLewis
Subject: Re: Pressure Profiling Update 3
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On 30, 8:34 am, "Jack Denver" <nunuv...@netscape.net > wrote:
> "jim schulman" <jim_schul...@ameritech.net> wrote in message
> > On my new Elektra, adding an OPV made absolutely no difeence to the
> > taste, even when I was tasting unblind and with an expectation of big
> > improvements -- anything from 8 bar to 14 produces roughly identical
> > flow and taste characteristics. These machines have a double
> > dispersion block with lots of very thin holes (3 stands of 18 ga
> > wire), which creates a straight down shower spray of water. I also
> > leave lots of headroom.
>
> It has often occured to me that seemingly trivial (and inexpensive) changes
> like using deeper basket can have as big an impact as changing the whole
> machine. I'm still not picturing what your "double" dispersion block looks
> like (picture is worth 1000 words). Is this just a screw in disk that sits
> in between the bottom of the group head and the shower screen? How many
> holes are there? I wonder if this part is available to purchase from
> Elektra or could you do the same thing by soldering shut the large holes in
> a regular dispersion disk and drilling a bunch of smaller holes?
Hi Jack,
I can't speak to Jim's Electra, but from pictures I've seen it looks
like my Techno. The water comes down into a shallow plenum. The exit
from that consists of six or eight (I forget) small vertical holes in
a brass disc that's probably about 3 mm thick. Below that is a
stainless screen covered with holes that are around 0.5 mm, and below
that is the stainless mesh of the final dispersion screen. The latter
two are formed into a unit. A standard 5 mm stainless flat-head screw
comes up from the bottom and holds the brass disk and screen into the
head. The result is a very even flow.
Best,
David
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Date: 30 Mar 2007 10:56:04
From: DavidMLewis
Subject: Re: Pressure Profiling Update 3
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On 29, 6:26 pm, "gscace" <gregory.sc...@nist.gov > wrote:
> Oh, yeah. One other thing that I want to try is to use a shallower
> basket than the LM ridgeless double, maybe like the Faema double
> basket, but with steeper walls. I'm thinking that the shallow cake
> with full 58mm width might promote clarity over deeper baskets since
> the radial temperature gradient in the cake will be less during the
> early phases of brewing. Barry and I talked about building a variable
> depth basket for just these sorts of shenanigans.
>
Hi Greg,
Very impressive. I don't think I understand, though, the difference
between the baskets that you're referring to here. Is it that if you
down-dose the LM basket, say with a curved scraper, you have
relatively more of the cake in the curved portion at the bottom?
By the way, a confounding factor in the Swift baskets is that the
holes are larger, or at least that's my understanding from the dealer.
Best,
David
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Date: 30 Mar 2007 06:59:37
From: gscace
Subject: Re: Pressure Profiling Update 3
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On 30, 2:35 am, "Paul Pratt" <p...@just-java.com > wrote:
> On 30, 9:26 am, "gscace" <gregory.sc...@nist.gov> wrote:
>
>
>
> > On 29, 5:08 pm, "Ken Fox"
>
> > <morceaudemerdeThisMerdeG...@hotmail.com> wrote:
> > > "gscace" <gregory.sc...@nist.gov> wrote in message
>
> > >news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
> > > Pressure Profiling Update 3
>
> > > >>>I think I'm homing in on some concrete information about pressure
> > > >>>profiling that is worth blabbing on about, so here goes:
>
> > > Hi Greg,
>
> > > This is all very interesting. I am wondering, however, to what extent your
> > > observations might be dose-dependent.
>
> > > In shot timing, the dosing of the basket (in my experience) trumps the other
> > > factors such as grind and tamping. Therefore, your observations might be
> > > valid for your style of dosing and not transferable (or requiring
> > > modification) for other dose levels. In addition, there might be interplay
> > > with your grinder type, e.g. planar vs. conical vs. mixed (DRM).
>
> > > What kind of baskets are you using and how much coffee are you putting into
> > > them? Which grinder?
>
> > > ken
>
> > Oh, yeah. One other thing that I want to try is to use a shallower
> > basket than the LM ridgeless double, maybe like the Faema double
> > basket, but with steeper walls. I'm thinking that the shallow cake
> > with full 58mm width might promote clarity over deeper baskets since
> > the radial temperature gradient in the cake will be less during the
> > early phases of brewing. Barry and I talked about building a variable
> > depth basket for just these sorts of shenanigans.
>
> > -Greg-
>
> Greg sounds like what you are looking for are some of the LM Swift
> baskets. 58mm straight sides but depth is shallower.
>
> >From the inside bottom of the basket (bottom of coffee cake) to the
>
> exterior rim (that touches the group gasket) I have...
>
> Standard Triple 26.5mm
> Std Double 23mm
> A sshallow wift basket 18mm
>
> Paul
Thanks!! Just what I needed to learn.
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Date: 30 Mar 2007 06:59:02
From: gscace
Subject: Re: Pressure Profiling Update 3
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On 29, 8:42 pm, "Ken Fox"
<morceaudemerdeThisMerdeG...@hotmail.com > wrote:
> "gscace" <gregory.sc...@nist.gov> wrote in message
>
> news:1175218008.958165.210280@r56g2000hsd.googlegroups.com...
>
>
>
> > Oh, yeah. One other thing that I want to try is to use a shallower
> > basket than the LM ridgeless double, maybe like the Faema double
> > basket, but with steeper walls. I'm thinking that the shallow cake
> > with full 58mm width might promote clarity over deeper baskets since
> > the radial temperature gradient in the cake will be less during the
> > early phases of brewing. Barry and I talked about building a variable
> > depth basket for just these sorts of shenanigans.
>
> > -Greg
>
> I'm just trying to point out that (in my view) all this stuff is connected.
> In the same way that I questioned whether Jim and my observations last year
> about needing 3+ bar to preinfuse, would produce the same observable results
> in the puck were the dose different (we used ~18g but Jim is now using
> mostly less than that), I think that your observations are going to be dose
> and technique and PF dependant. Jim may disagree; I had a little trouble
> deciphering his response to what I wrote in this same vein, to an earlier
> one of your (Greg's) posts on this issue.
>
> I do not want to puncture any nascent theories. I just want to point out
> that at the end of your testing it may be that all you can say that others
> will find to be repeatable, is that there is a list of variables that are
> important and interrelated, and that there is a huge YMMV factor there that
> is dependent on how others dose into what sort of gear, with what type of
> grinder, and that the wheel might have to be reinvented by all those who try
> to extrapolate your results unless they have the same gear and do things in
> the same way, as you do.
>
> Thanks for your efforts and keep us informed . . . .
>
> ken
Maybe. But I don't think so. Feel free to come over and play with
it. We have comfortable digs, although at lower altitude than you are
used to.
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Date: 30 Mar 2007 09:28:51
From: Ken Fox
Subject: Re: Pressure Profiling Update 3
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"gscace" <gregory.scace@nist.gov > wrote in message
news:1175263142.936168.89640@p15g2000hsd.googlegroups.com...
> >
> Maybe. But I don't think so. Feel free to come over and play with
> it. We have comfortable digs, although at lower altitude than you are
> used to.
>
I'll take you up on the offer when I'm in the area, Greg. . . .
Your short response was not really responsive to the several issues that I
raised. Are you saying that you don't think that what you are observing is
dose or equipment or technique dependant? All of my prior experience with
dosing, brew pressures, pre-infusion, equipment and machine mods, plus to
some extent other barista-type techniques, leads me to beg to differ.
If you can get your observations down to the point where there is something
VERY straightforward that you can test in a blind tasting fashion, I would
encourage you to do so. I think it will be hard to do this with a
one-of-a-kind machine, but perhaps you can develop a scoring system that
will allow this. In any event, you will need to focus on just one variable
for each test, or risk having the various variables cancel each other out
and not end up being able to conclude much of anything.
Good luck, and keep us informed.
ken
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Date: 30 Mar 2007 06:42:10
From: gscace
Subject: Re: Pressure Profiling Update 3
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Hi Jim:
Comments imbedded.
>
> I really have no clue how pressure interacts with dosing level.
>
> On my new Elektra, adding an OPV made absolutely no difeence to the
> taste, even when I was tasting unblind and with an expectation of big
> improvements -- anything from 8 bar to 14 produces roughly identical
> flow and taste characteristics. These machines have a double
> dispersion block with lots of very thin holes (3 stands of 18 ga
> wire), which creates a straight down shower spray of water. I also
> leave lots of headroom.
>
> The E61 head has a single 45 degree angle channel into two large
> holes, and water stream is very asconce. I also packed it up to the
> screen. This produiced excessively bitter short (high pressure on a
> vibe) shots until I went to around 8.75 (panel guage) brew pressure,
> at which point he shots became very good
>
> The old LMs are perhaps the most prima-donna-ish machines in
> existence. It's no surprise they show great sensitivity to preinfusion
> and initial pressure variations, after all, they show great
> sensitivity to just about anything else one can do with coffee or
> brewing.
>
> 1. The initial profile of preinfusion length, and starting pressure,
> along with dosing and head space levels, may determine how well the
> puck settles, and the details of this may not show up in the naked
> extraction. This will be very machine dependent, and the early part of
> an optimum pressure profile will vary by machine and dose. It will
> also be that some machines are simply more sensitive than others to
> variations at this stage.
>
I completely agree with this.
> 2. I found that the fines at the bottom seem to act as a storage
> element of the solubles; they increase their solubles content in the
> early part of the shot, storing the coffee extracted from the puck
> top. Since this fraction extracts later in the shot, after the puck is
> settled, the optimum profile late in the shot will be universal for
> all machines. One can compensate for a non-optimum pressures by
> stopping on color and letting the shot time and volume vary from shot
> to shot, but I don't have any doubt that a pressure profile could
> improve on this.
I used to be very careful to stop brewing when blonding appeared
because blonding was a good visual clue that bitter tastes were on the
way. This is not the case so much now. Makes discerning when to stop
brewing a more subjective process. Now, rather than using visual
clues I'm relying on taste and collected volume. It's a bit of an
adjustment.
-Greg
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Date: 30 Mar 2007 06:33:31
From: gscace
Subject: Re: Pressure Profiling Update 3
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On 30, 5:01 am, sprsso <acrit...@cfl.rr.com > wrote:
> I may have the portafilter you're looking for already. Early Cimbali
> attempts to adapt for the pod used a 58mm portafilter with threaded
> height adjustment for the basket to tighten up on a given
> manufacturer's pods. The range was quite wide as I recall. I'll look
> for it this weekeng....al
>
>
>
> >Oh, yeah. One other thing that I want to try is to use a shallower
> >basket than the LM ridgeless double, maybe like the Faema double
> >basket, but with steeper walls. I'm thinking that the shallow cake
> >with full 58mm width might promote clarity over deeper baskets since
> >the radial temperature gradient in the cake will be less during the
> >early phases of brewing. Barry and I talked about building a variable
> >depth basket for just these sorts of shenanigans.
>
> >-Greg
Hey thanks! If I can shove it onto a zocco that would be very
helpful!
-Greg
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Date: 30 Mar 2007 03:50:06
From: gscace
Subject: Re: Pressure Profiling Update 3
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On 30, 2:50 am, Danny <d...@nospam.gaggia-espresso.com > wrote:
> Danny wrote:
> > So spring levers (with their declining pressure curve) may actually be
> > spot on.
>
> -snip-
>
> Excuse the bad form, but from reading the rest of the thread, you
> wouldn't find my results "spot on" since you don't think a linear
> pressure reduction is desirable.
>
> --
> Regards, Danny
>
> http://www.gaggia-espresso.com(a purely hobby site)
I think it's in the right direction, and while not optimum, it's a
happy accident that's close and maybe close enuff.
-Greg
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Date: 30 Mar 2007 08:46:35
From: Danny
Subject: Re: Pressure Profiling Update 3
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gscace wrote:
> Pressure Profiling Update 3
>
> I think I'm homing in on some concrete information about pressure
> profiling that is worth blabbing on about, so here goes:
>
> First thing is that there seems to be a practical maximum pressure
> value beyond which things go to hell in a handbasket tastebudswise. I
> found this out when I was experimenting with pressure profiles that
> included a high-pressure hump at the beginning of the extraction.
> Values for the hump were as high as 165 psi (11.3 bar). My thinking
> was that if sweetness was extracted early in the brewing process, then
> maybe I could emphasize it by increasing pressure to a high value
> early on, reducing to more conventional values later. The result was
> that I extracted crema that was kedly bitter. Bitterness was muted
> by reducing the magnitude of the hump. Bitterness was removed once
> the max pressure value was reduced to 9.5 bars at the coffee cake,
> which adds credence to the conventional 9-bar wisdom. I learned later
> that Jim Schulman has also observed this effect. I also successfully
> replicated the effect for Peter Lynagh, of Terroir Coffee, when he
> came down to visit.
>
> Once I learned that there was a maximum practical brewing pressure, I
> began to think of pressure profiling in terms of the minimization of
> undesirable tastes, rather than in terms of super-extracting desired
> compounds. Taste tests with Nick Cho demonstrated to me that the
> sweet tastes and mouthfeel are developed early in the brew process,
> with dilution occurring later. Unfortunately, in the tests mit Cho
> (gesundheit!) extraction of bitter compounds also occurred during the
> dilution phase, meaning that a balance needed to be struck between
> dilution of the drink to a desired volume and introduction of negative
> taste components. Reducing the brewing pressure as brewing progresses
> seems to be beneficial in reducing bitter tastes extracted during the
> dilution phase. Tests with Nick pointed to accentuated sweetness in
> Counter Culture Toscana, which in retrospect was really a subtraction
> of bitter components added in the last third of the brew process.
>
> The most successful general profile that I have come up with to date
> (I've now got an excel file with a bazillion profiles mapped out in
> it) is a pressure profile in which the pressure rapidly increases from
> some nominal start value to 9 bars at the group (elapsed time of 1
> second from start to full pressure) with a short 9 bar soak, then
> ramps downward in a slow linear fashion (straight line degradation) to
> around 7 ½ bar, with a more rapid, second-order (curved downward)
> slope over the last few seconds to around 6 bar, arriving at 6 bar 30
> seconds after initiation of the brew cycle. This general shape can be
> used with or without a pre-infusion step. The pre-infusion that I've
> been using is to soak the cake at around 2 - 3 bar for 3 seconds, then
> quickly ramping to maximum value with an exponentially increasing
> slope. Full pressure is attained 3 seconds after the end of the low-
> pressure soak. This combination produces liquid evenly over the
> bottom of the filter basket almost as soon as the pressure begins its
> rapid increase. Regardless of whether or not pre-infusion is used,
> I've been using a very similar profile toward the end of the brewing
> period. If pre-infusion is not used, I increase the time of the high-
> pressure soak by a few seconds.
>
> It seems to me that the efficacy of preinfusion is coffee specific.
> There are three basic coffees that I've inflicted pressure profiling
> upon and with which I can comment. I've been drinking dry-processed
> Ethiopian SOs, and Ethiopian-based simple blends that have a lot of
> mouthfeel and body. My tests with Nick used Counterculture Toscano.
> I don't really know what is in it, and for the purposes of this
> discussion I don't think I really need to know. And last weekend,
> Peter Lynagh and I concentrated on a very lightly roasted Brazil.
> Here's a link to Terroir's information about the coffee:
>
> http://info.terroircoffee.com/content/view/17/2/
>
> For brewing temps, the Ethipian DP and Toscano seem to like around
> 201F. The SO Brazil was brewed at 195 F. The blends seem at first
> blush to benefit from preinfusion. I think that the soak and
> subsequent rapid pressure ramp may produce more mouthfeel, but I need
> to revisit this as I haven't been systematic enough, particularly in
> light of our results with the Brazil. We found that pre-infusion was a
> waste of extraction time when brewing the SO Brazil. Unlike the
> blends, the SO Brazil produced two predominate tastes with great
> clarity - nuts and sweetness reminiscent of dried figs. Both
> nuttiness and sweetness were enhanced when the pre-infusion step was
> removed. The clarity of the Brazil made differences between brewing
> at constant pressure and brewing with profiled pressure easy to
> discern. Bitter tastes were evident with constant-pressure brewing
> and demonstrably removed by profiling.
>
> Recently folks have come up to me on the street, shoving their pudgy
> fingers in my puny chest, demanding to know that if pressure profiling
> meant deemphasizing the last portion of the brewing process, why not
> just stop brewing early? After I imagine breaking their finger with a
> deft ital arts-type motion, I counter with the argument that early
> brew termination is different. Compare two shots of the same volume,
> but with one brewed in the style of brewtus interruptus, and the other
> brewed to satisfying completion with pressure profiling. If one
> terminates early, for example at 18 secs in a 27 sec extraction, the
> volumetric flow rate during the 18 second period is much faster than
> the flow rate for an extraction taking place over the entire period.
> The extractions that we are observing with profiled pressure have more
> or less constant flow rate throughout the entire time period, which
> means that the volumetric flow rate is less by 50%, but over a longer
> time period. This changes the taste.
>
> As I try different coffees and gain more experience I'm getting more
> confident that pressure is worth exploring as a brew parameter. There
> is still a lot to learn here, but the tests with Terroir indicate that
> variable pressure is useful when one is brewing clean SO espressos in
> which one or two tastes are showcased. I'm not sure which cart drives
> which horse when it comes to blends. I don't know if various widely
> used pre-infusion schemes were developed because they work with
> traditional blends, or if blends end up being developed to mask
> machine deficiencies. My cynical self thinks it's the latter. I have
> a lot more to learn about this, and it gets more difficult when I'm
> using coffees I've munged together. I don't feel like I'm a good
> enough roaster or blending dude to come up with confident conclusions,
> other than to go back with what I learned about the Brazil SO and see
> if I can make any hay with the stuff I usually drink. That means I'm
> not close to closure, which means that if you all don't behave, rather
> than dislocate your digits I'll spring Pressure Profiling Update 4 on
> you.
>
So spring levers (with their declining pressure curve) may actually be
spot on. My own research with my springs inidicate a starting and
ending pressure (after preinfusion) as follows, copied from a previous
thread:
Exchanged several emails with a professor there (Portsmouth
University), which culminated in him popping by for a coffee, bringing
with him the results of his
calculation based on the spring and piston details I'd provided.
Although the spring details are precise, the piston dimension is an
educated guess. since I wasn't in a position to get at one easily.
Looking at the image on the website shows the piston to be around the
same diameter as the spring - 47mm or so. He used these figures to come
up with the following (and I bet all my nice formatting stuff is lost
(¶ = Pi))...
Piston area = ¶D2
-------
4
= ¶(.047)2 m2
------------
4
= 1.735 x 10 –3 m2
------------------
Max spring force = 2640 N
Min spring force = 1620 N
Max pressure = 2640
-------
1.735 x 106 N/ m2
= 1.522 x 106 Pa (N/ m2)
Min pressure = 1620
------
1.735 x 10-3 N/ m2
= 0.933 x 106 Pa
1000 Pa = 1 bar
Therefore Max pressure = 15.22 bar
Min pressure = 9.33 bar
In practice, and with a worn spring, I think real world meaurements
(if I had a Scace device) would should a starting pressure of 10-11
bar and a finishing pressure of around 7 bar. I have many groups'
worth of spring levers, and would like to measure the difference
between them, since they have kedly different usage/wear.
I have since measured a piston and found it to be 52.7mm diameter, so
the above calcs need to be redone with this info.
--
Regards, Danny
http://www.gaggia-espresso.com (a purely hobby site)
|
| | |
Date: 30 Mar 2007 08:50:06
From: Danny
Subject: Re: Pressure Profiling Update 3
|
Danny wrote:
> So spring levers (with their declining pressure curve) may actually be
> spot on.
-snip-
Excuse the bad form, but from reading the rest of the thread, you
wouldn't find my results "spot on" since you don't think a linear
pressure reduction is desirable.
--
Regards, Danny
http://www.gaggia-espresso.com (a purely hobby site)
|
| |
Date: 30 Mar 2007 00:35:48
From: Paul Pratt
Subject: Re: Pressure Profiling Update 3
|
On 30, 9:26 am, "gscace" <gregory.sc...@nist.gov > wrote:
> On 29, 5:08 pm, "Ken Fox"
>
>
>
>
>
> <morceaudemerdeThisMerdeG...@hotmail.com> wrote:
> > "gscace" <gregory.sc...@nist.gov> wrote in message
>
> >news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
> > Pressure Profiling Update 3
>
> > >>>I think I'm homing in on some concrete information about pressure
> > >>>profiling that is worth blabbing on about, so here goes:
>
> > Hi Greg,
>
> > This is all very interesting. I am wondering, however, to what extent your
> > observations might be dose-dependent.
>
> > In shot timing, the dosing of the basket (in my experience) trumps the other
> > factors such as grind and tamping. Therefore, your observations might be
> > valid for your style of dosing and not transferable (or requiring
> > modification) for other dose levels. In addition, there might be interplay
> > with your grinder type, e.g. planar vs. conical vs. mixed (DRM).
>
> > What kind of baskets are you using and how much coffee are you putting into
> > them? Which grinder?
>
> > ken
>
> Oh, yeah. One other thing that I want to try is to use a shallower
> basket than the LM ridgeless double, maybe like the Faema double
> basket, but with steeper walls. I'm thinking that the shallow cake
> with full 58mm width might promote clarity over deeper baskets since
> the radial temperature gradient in the cake will be less during the
> early phases of brewing. Barry and I talked about building a variable
> depth basket for just these sorts of shenanigans.
>
> -Greg-
Greg sounds like what you are looking for are some of the LM Swift
baskets. 58mm straight sides but depth is shallower.
>From the inside bottom of the basket (bottom of coffee cake) to the
exterior rim (that touches the group gasket) I have...
Standard Triple 26.5mm
Std Double 23mm
A sshallow wift basket 18mm
Paul
|
| |
Date: 29 Mar 2007 18:47:53
From: gscace
Subject: Re: Pressure Profiling Update 3
|
On 29, 7:42 pm, "Travesso" <cpaso...@hotmail.com > wrote:
> I tested my portable espresso machine --http://travesso.com/index-4.html
> -- with Nick. He thought that it was possible that the reason our
> simple little 4" unit was making such good espresso with a POD was
> that we had complete control over the pressure curve. We have
> complete control over the pressure curve, up or down, over the entire
> brew time.
> We did not show him the ground coffee version, but I really like
> having full control over the pressure.
>
> As a side, I think the Illy book states that at over 150PSI the coffee
> stabilizes itself. I have found that to be somewhat true. From a PSI
> of 180 to 250 (I went all the way to 1200PSI) I did not find a real
> difference. Please note, that all water stopped when I did this with
> ground coffee.
I read a paper that claimed the same thing as Illy. I didn't test
higher than what I mentioned in my diatribe because I didn't feel like
it was worth it. Taste was compromised. So I have nothing to support
or contradict Illy here. I suspect he's right enough, but the
conclusion is irrelevant. I think the 9 bar number does stand up to
scrutiny however.
On thing I like about Nick is that he's always interested in checking
out what folks are doing.
-Greg
|
| |
Date: 29 Mar 2007 18:41:33
From: gscace
Subject: Re: Pressure Profiling Update 3
|
On 29, 6:08 pm, "Jack Denver" <nunuv...@netscape.net > wrote:
> A couple of thoughts:
>
> 1. I wonder how your profile compares to a spring lever machine where the=
re
> is also an intitial hump and then a taper?
>
> 2. I also wonder whether, once you determine an optimum profile, whether=
it
> would be possible to implement it without fancy electronics - for example=
a
> relief valve with a motor driven cam (turning at 2 rpm) in the shape of =
the
> profile pressing against the relief spring?
>
> "gscace" <gregory.sc...@nist.gov> wrote in message
>
> news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
> Pressure Profiling Update 3
>
> I think I'm homing in on some concrete information about pressure
> profiling that is worth blabbing on about, so here goes:
>
> The most successful general profile that I have come up with to date
> (I've now got an excel file with a bazillion profiles mapped out in
> it) is a pressure profile in which the pressure rapidly increases from
> some nominal start value to 9 bars at the group (elapsed time of 1
> second from start to full pressure) with a short 9 bar soak, then
> ramps downward in a slow linear fashion (straight line degradation) to
> around 7 =BD bar, with a more rapid, second-order (curved downward)
> slope over the last few seconds to around 6 bar, arriving at 6 bar 30
> seconds after initiation of the brew cycle. This general shape can be
> used with or without a pre-infusion step. The pre-infusion that I've
> been using is to soak the cake at around 2 - 3 bar for 3 seconds, then
> quickly ramping to maximum value with an exponentially increasing
> slope. Full pressure is attained 3 seconds after the end of the low-
> pressure soak. This combination produces liquid evenly over the
> bottom of the filter basket almost as soon as the pressure begins its
> rapid increase. Regardless of whether or not pre-infusion is used,
> I've been using a very similar profile toward the end of the brewing
> period. If pre-infusion is not used, I increase the time of the high-
> pressure soak by a few seconds.
Actually one of my first thoughts when embarking on this mess was to
see if there was any credence to the idea that lever machines had some
magic espresso bullet because of their pressure profiles. Paul Pratt
was kind enough to send me the values for his lever machine, and I
tried them but decided that other values were better for what I was
doing. His machine goes to 8 bar and then down to 3 at the end of the
extraction. Spring-operated lever machine profiles have linear
pressure reduction with time unless progressively would springs are
used, or there are games played with geometry. I view the benefit of
linear reduction as nothing more than a happy accident. I'm thinking
that optimal profiles are more curved, and don't necessarily always
slope downward in the beginning. I'm not planning on trying to prove
it.
While the system that I built is very tuneable, it is also extremely
robust. It's also not cheap. I think in a production world one would
do it differently. I'm a mechanical engineer, not a hardware
designer, so the thing is done in a way that will work well for an
espresso lab. Before implementing a production system for a machine
with a large distribution I think it would be a very good idea to
investigate linking pressure to flow instead of time.
WRT cost reduction you might not need a transducer, but one of the
nice things about my system is that pressure space is very flexible,
easily tuned and accurate. Removal of feedback systems in an effort
to save money might reduce benefit.
|
| |
Date: 29 Mar 2007 18:26:49
From: gscace
Subject: Re: Pressure Profiling Update 3
|
On 29, 5:08 pm, "Ken Fox"
<morceaudemerdeThisMerdeG...@hotmail.com > wrote:
> "gscace" <gregory.sc...@nist.gov> wrote in message
>
> news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
> Pressure Profiling Update 3
>
> >>>I think I'm homing in on some concrete information about pressure
> >>>profiling that is worth blabbing on about, so here goes:
>
> Hi Greg,
>
> This is all very interesting. I am wondering, however, to what extent your
> observations might be dose-dependent.
>
> In shot timing, the dosing of the basket (in my experience) trumps the other
> factors such as grind and tamping. Therefore, your observations might be
> valid for your style of dosing and not transferable (or requiring
> modification) for other dose levels. In addition, there might be interplay
> with your grinder type, e.g. planar vs. conical vs. mixed (DRM).
>
> What kind of baskets are you using and how much coffee are you putting into
> them? Which grinder?
>
> ken
Oh, yeah. One other thing that I want to try is to use a shallower
basket than the LM ridgeless double, maybe like the Faema double
basket, but with steeper walls. I'm thinking that the shallow cake
with full 58mm width might promote clarity over deeper baskets since
the radial temperature gradient in the cake will be less during the
early phases of brewing. Barry and I talked about building a variable
depth basket for just these sorts of shenanigans.
-Greg
|
| | |
Date: 30 Mar 2007 06:01:11
From: sprsso
Subject: Re: Pressure Profiling Update 3
|
I may have the portafilter you're looking for already. Early Cimbali
attempts to adapt for the pod used a 58mm portafilter with threaded
height adjustment for the basket to tighten up on a given
manufacturer's pods. The range was quite wide as I recall. I'll look
for it this weekeng....al
>
>Oh, yeah. One other thing that I want to try is to use a shallower
>basket than the LM ridgeless double, maybe like the Faema double
>basket, but with steeper walls. I'm thinking that the shallow cake
>with full 58mm width might promote clarity over deeper baskets since
>the radial temperature gradient in the cake will be less during the
>early phases of brewing. Barry and I talked about building a variable
>depth basket for just these sorts of shenanigans.
>
>-Greg
|
| | |
Date: 29 Mar 2007 19:42:52
From: Ken Fox
Subject: Re: Pressure Profiling Update 3
|
"gscace" <gregory.scace@nist.gov > wrote in message
news:1175218008.958165.210280@r56g2000hsd.googlegroups.com...
> >
> Oh, yeah. One other thing that I want to try is to use a shallower
> basket than the LM ridgeless double, maybe like the Faema double
> basket, but with steeper walls. I'm thinking that the shallow cake
> with full 58mm width might promote clarity over deeper baskets since
> the radial temperature gradient in the cake will be less during the
> early phases of brewing. Barry and I talked about building a variable
> depth basket for just these sorts of shenanigans.
>
> -Greg
>
I'm just trying to point out that (in my view) all this stuff is connected.
In the same way that I questioned whether Jim and my observations last year
about needing 3+ bar to preinfuse, would produce the same observable results
in the puck were the dose different (we used ~18g but Jim is now using
mostly less than that), I think that your observations are going to be dose
and technique and PF dependant. Jim may disagree; I had a little trouble
deciphering his response to what I wrote in this same vein, to an earlier
one of your (Greg's) posts on this issue.
I do not want to puncture any nascent theories. I just want to point out
that at the end of your testing it may be that all you can say that others
will find to be repeatable, is that there is a list of variables that are
important and interrelated, and that there is a huge YMMV factor there that
is dependent on how others dose into what sort of gear, with what type of
grinder, and that the wheel might have to be reinvented by all those who try
to extrapolate your results unless they have the same gear and do things in
the same way, as you do.
Thanks for your efforts and keep us informed . . . .
ken
|
| | | |
Date: 30 Mar 2007 02:07:52
From: jim schulman
Subject: Re: Pressure Profiling Update 3
|
On Thu, 29 2007 19:42:52 -0600, "Ken Fox"
<morceaudemerdeThisMerdeGoes@hotmail.com > wrote:
>I'm just trying to point out that (in my view) all this stuff is connected.
>In the same way that I questioned whether Jim and my observations last year
>about needing 3+ bar to preinfuse, would produce the same observable results
>in the puck were the dose different (we used ~18g but Jim is now using
>mostly less than that), I think that your observations are going to be dose
>and technique and PF dependant. Jim may disagree; I had a little trouble
>deciphering his response to what I wrote in this same vein, to an earlier
>one of your (Greg's) posts on this issue.
I really have no clue how pressure interacts with dosing level.
On my new Elektra, adding an OPV made absolutely no difeence to the
taste, even when I was tasting unblind and with an expectation of big
improvements -- anything from 8 bar to 14 produces roughly identical
flow and taste characteristics. These machines have a double
dispersion block with lots of very thin holes (3 stands of 18 ga
wire), which creates a straight down shower spray of water. I also
leave lots of headroom.
The E61 head has a single 45 degree angle channel into two large
holes, and water stream is very asconce. I also packed it up to the
screen. This produiced excessively bitter short (high pressure on a
vibe) shots until I went to around 8.75 (panel guage) brew pressure,
at which point he shots became very good
The old LMs are perhaps the most prima-donna-ish machines in
existence. It's no surprise they show great sensitivity to preinfusion
and initial pressure variations, after all, they show great
sensitivity to just about anything else one can do with coffee or
brewing.
So here's my (probably very wrong) prediction on how this will play
out
1. The initial profile of preinfusion length, and starting pressure,
along with dosing and head space levels, may determine how well the
puck settles, and the details of this may not show up in the naked
extraction. This will be very machine dependent, and the early part of
an optimum pressure profile will vary by machine and dose. It will
also be that some machines are simply more sensitive than others to
variations at this stage.
2. I found that the fines at the bottom seem to act as a storage
element of the solubles; they increase their solubles content in the
early part of the shot, storing the coffee extracted from the puck
top. Since this fraction extracts later in the shot, after the puck is
settled, the optimum profile late in the shot will be universal for
all machines. One can compensate for a non-optimum pressures by
stopping on color and letting the shot time and volume vary from shot
to shot, but I don't have any doubt that a pressure profile could
improve on this.
|
| | | | |
Date: 30 Mar 2007 11:34:31
From: Jack Denver
Subject: Re: Pressure Profiling Update 3
|
"jim schulman" <jim_schulman@ameritech.net > wrote in message
news:t0cp03d7lj3rhrsogocipk4205d1uc284m@4ax.com...
> On Thu, 29 2007 19:42:52 -0600, "Ken Fox"
> <morceaudemerdeThisMerdeGoes@hotmail.com> wrote:
>
>
> On my new Elektra, adding an OPV made absolutely no difeence to the
> taste, even when I was tasting unblind and with an expectation of big
> improvements -- anything from 8 bar to 14 produces roughly identical
> flow and taste characteristics. These machines have a double
> dispersion block with lots of very thin holes (3 stands of 18 ga
> wire), which creates a straight down shower spray of water. I also
> leave lots of headroom.
>
> The E61 head has a single 45 degree angle channel into two large
> holes, and water stream is very asconce. I also packed it up to the
> screen. This produiced excessively bitter short (high pressure on a
> vibe) shots until I went to around 8.75 (panel guage) brew pressure,
> at which point he shots became very good
>
> The old LMs are perhaps the most prima-donna-ish machines in
> existence. It's no surprise they show great sensitivity to preinfusion
> and initial pressure variations, after all, they show great
> sensitivity to just about anything else one can do with coffee or
> brewing.
>
It has often occured to me that seemingly trivial (and inexpensive) changes
like using deeper basket can have as big an impact as changing the whole
machine. I'm still not picturing what your "double" dispersion block looks
like (picture is worth 1000 words). Is this just a screw in disk that sits
in between the bottom of the group head and the shower screen? How many
holes are there? I wonder if this part is available to purchase from
Elektra or could you do the same thing by soldering shut the large holes in
a regular dispersion disk and drilling a bunch of smaller holes?
|
| | | | | |
Date: 30 Mar 2007 13:44:18
From: jim schulman
Subject: Re: Pressure Profiling Update 3
|
On Fri, 30 2007 11:34:31 -0400, "Jack Denver"
<nunuvyer@netscape.net > wrote:
>I'm still not picturing what your "double" dispersion block looks
>like (picture is worth 1000 words).
>http://i12.photobucket.com/albums/a240/jim_schulman/Elektra/MicroCasaSemiAuto2lr.jpg
part 22 is the actual dispersion block, but the group bell, 20, has
it's own set of holes. Part 22 might fit into other groups.
Although Greg reports better results with the shallow Rancilio basket
when low dosing (the NS double basket is similar), I think that if
there's problems with water dispersion and pressure, going to a triple
basket may help, since this gives extra headspace and more of a
preinfusion. Here's a graph of dwell time versus dose using a triple
>http://www.home-barista.com/forums/userpix/18_dose_versus_dwell_1.gif
The counterargument is that the headspace becomes filled with brewed
coffee, and that this fraction of the puck is lost to the cup.
Petracco, in Illy and other papers, says the puck behaves very
"non-linearly" early in the shot as the fines settles and the grind
particles soak, swell, and interlock into an aggregate. This probably
implies that the fine structure of the puck may depend sensitively on
all sorts of little things that happen before one sees the first drop.
|
| | | | | | |
Date: 30 Mar 2007 15:14:35
From: Jack Denver
Subject: Re: Pressure Profiling Update 3
|
This looks better than the setup in my Oscar, but not hugely so.
In the Oscar the hot water leaves the underside of the group thru a single
hole, while you get 5, so that's a step up. Then there's a brass disc almost
like your 22 but with 8 holes and 23 is a sandwich - a thin metal disk with
a whole bunch of fairly big holes and a mesh screen. When you referred to
many fine hole did you mean #23 and is your 23 screen material or drilled
sheet metal or a sandwich? I've also wondered what is the point of making
22 as thick as it is. It has to be 3 dimensional to form a "well" under the
exit holes of the group but it seems to be thicker than it needs to be.
And then there is the famous "French" group of the Diva where the water
shoots out sideways in all directions instead of down.
"jim schulman" <jim_schulman@ameritech.net > wrote in message
news:sjlq03hfdn042a1tjkd5kfkopeoqnqgq3v@4ax.com...
> On Fri, 30 2007 11:34:31 -0400, "Jack Denver"
> <nunuvyer@netscape.net> wrote:
>
>>I'm still not picturing what your "double" dispersion block looks
>>like (picture is worth 1000 words).
>
>>http://i12.photobucket.com/albums/a240/jim_schulman/Elektra/MicroCasaSemiAuto2lr.jpg
>
> part 22 is the actual dispersion block, but the group bell, 20, has
> it's own set of holes. Part 22 might fit into other groups.
>
> Although Greg reports better results with the shallow Rancilio basket
> when low dosing (the NS double basket is similar), I think that if
> there's problems with water dispersion and pressure, going to a triple
> basket may help, since this gives extra headspace and more of a
> preinfusion. Here's a graph of dwell time versus dose using a triple
>
>>http://www.home-barista.com/forums/userpix/18_dose_versus_dwell_1.gif
>
> The counterargument is that the headspace becomes filled with brewed
> coffee, and that this fraction of the puck is lost to the cup.
>
> Petracco, in Illy and other papers, says the puck behaves very
> "non-linearly" early in the shot as the fines settles and the grind
> particles soak, swell, and interlock into an aggregate. This probably
> implies that the fine structure of the puck may depend sensitively on
> all sorts of little things that happen before one sees the first drop.
|
| | | | | | | |
Date: 30 Mar 2007 15:44:49
From: jim schulman
Subject: Re: Pressure Profiling Update 3
|
On Fri, 30 2007 15:14:35 -0400, "Jack Denver"
<nunuvyer@netscape.net > wrote:
>In the Oscar the hot water leaves the underside of the group thru a single
>hole, while you get 5, so that's a step up. Then there's a brass disc almost
>like your 22 but with 8 holes and 23 is a sandwich - a thin metal disk with
>a whole bunch of fairly big holes and a mesh screen.
I'm not sure what the extra block in the group bell does. The holes do
not align with the ones in actual block, instead the water goes into a
circular trough and then feeds through the holes. The arrangement is
the same on all Elektra's 58mm groups.
>When you referred to
>many fine hole did you mean #23 ...
D'oh, a case of 1, 2, 3. many. I was referring to 22.
> I've also wondered what is the point of making
>22 as thick as it is. It has to be 3 dimensional to form a "well" under the
>exit holes of the group but it seems to be thicker than it needs to be.
The thickness of the block and the narrow diameter of the holes means
it clogs easily and is a pain to clean out. Fregnan, the owner of
Elektra, has a reputation of having somewhat odd and very strongly
held opinions -- this may be one of them. In this case, it seems to
work. The Elektra groups, use very wide gicleurs (0.9 or 0.7mm) and
dosed at mamximum, have very short dwell times; but are still well
behaved in terms of channeling, body, and taste clarity.
>
>And then there is the famous "French" group of the Diva where the water
>shoots out sideways in all directions instead of down.
I think the overall idea of all these arrangements is to get the water
inflow gentle enough so that during the time the puck absorbs water
and swells, the surface isn't damaged, and pinholes don't develop. The
obvious test of this is is to stop the shot and remove the puck when
the first drops appear. If it's fully soaked, fully expanded, and well
meshed together, the dispersion design is good.
There's probably lots of ways of skinning this particular cat, but
probably lots of ways of getting it wrong too. I know that people who
really are particlura about drip coffee makers are mostly dissatisfied
with the way they disperse the water.
|
| | | | | | | | |
Date: 30 Mar 2007 19:17:36
From: Jack Denver
Subject: Re: Pressure Profiling Update 3
|
No, it's not just Elektra - I haven't compared them side by side but the
block on my NS is also thicker than it would appear to need to be for its
function and judging from the drawing about the same thickness. Could it be
that they are purposely taking up space so to get the shower screen down
closer to the top of the puck and not leaving headspace which as you said
would end up filled with brewed coffee? Or they are adding more thermal mass
to the group? There must be some good reason for it because manufacturers
are no know for building parts heavier than they need to be.
"jim schulman" <jim_schulman@ameritech.net > wrote in message
news:qpsq03p6590tcu03p0l57opit7bk0c4ch9@4ax.com...
>>
>
> The thickness of the block and the narrow diameter of the holes means
> it clogs easily and is a pain to clean out. Fregnan, the owner of
> Elektra, has a reputation of having somewhat odd and very strongly
> held opinions -- this may be one of them.
|
| | | | | | | | | |
Date: 31 Mar 2007 20:16:50
From: Barry Jarrett
Subject: Re: Pressure Profiling Update 3
|
On Fri, 30 2007 19:17:36 -0400, "Jack Denver"
<nunuvyer@netscape.net > wrote:
>No, it's not just Elektra - I haven't compared them side by side but the
>block on my NS is also thicker than it would appear to need to be for its
>function and judging from the drawing about the same thickness. Could it be
>that they are purposely taking up space so to get the shower screen down
>closer to the top of the puck and not leaving headspace which as you said
>would end up filled with brewed coffee? Or they are adding more thermal mass
>to the group? There must be some good reason for it because manufacturers
>are no know for building parts heavier than they need to be.
>
could it be a fluid dynamics issue, with the ratio of orifice diameter
to length has a particular influence on the way the water passes
through the orifice?
|
| | | | | | | | | | |
Date: 04 Apr 2007 07:25:15
From: Dan Bollinger
Subject: Re: Pressure Profiling Update 3
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> could it be a fluid dynamics issue, with the ratio of orifice diameter
> to length has a particular influence on the way the water passes
> through the orifice?
Flow through a short tube is more laminar and results in a stream. While flow
exiting a thin sheet orifice of the same diameter and pressure is more
turbulent.
Hurricanes for candles and kerosene lanterns take advantage of this effect. The
shield has many small holes (orifices) and the turbulent flow tends to negate
each other so the flame isn't extinguished by one, big puff.
Dan
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Date: 31 Mar 2007 17:32:41
From: Jack Denver
Subject: Re: Pressure Profiling Update 3
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Maybe except it seems to me a thicker (longer) passage would create more of
a focused jet, which is the opposite of what you want. I think something
like a stainless scrubber would be ideal:
http://www.acet.com/graphics/00000001/products/ACS434PB.jpg
so that the water loses any momentum it has from shooting out of any
individual holes.
"Barry Jarrett" <barry@rileys-coffee.com > wrote in message
news:81gt03tl6smqa7hbh8mtthks11dgvsmjeu@4ax.com...
> On Fri, 30 2007 19:17:36 -0400, "Jack Denver"
> <nunuvyer@netscape.net> wrote:
>
> >No, it's not just Elektra - I haven't compared them side by side but the
> >block on my NS is also thicker than it would appear to need to be for its
> >function and judging from the drawing about the same thickness. Could it
> >be
> >that they are purposely taking up space so to get the shower screen down
> >closer to the top of the puck and not leaving headspace which as you said
> >would end up filled with brewed coffee? Or they are adding more thermal
> >mass
> >to the group? There must be some good reason for it because manufacturers
> >are no know for building parts heavier than they need to be.
> >
>
>
> could it be a fluid dynamics issue, with the ratio of orifice diameter
> to length has a particular influence on the way the water passes
> through the orifice?
>
>
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Date: 30 Mar 2007 19:47:28
From: jim schulman
Subject: Re: Pressure Profiling Update 3
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On Fri, 30 2007 19:17:36 -0400, "Jack Denver"
<nunuvyer@netscape.net > wrote:
>No, it's not just Elektra - I haven't compared them side by side but the
>block on my NS is also thicker than it would appear to need to be for its
>function and judging from the drawing about the same thickness. Could it be
>that they are purposely taking up space so to get the shower screen down
>closer to the top of the puck and not leaving headspace which as you said
>would end up filled with brewed coffee? Or they are adding more thermal mass
>to the group? There must be some good reason for it because manufacturers
>are no know for building parts heavier than they need to be.
You could be right. The block on the E61 is small, about the size and
thickness of a quarter. This does point to thermal management -- on
lighter weight or non thermosyphom groups, it may be designed to soak
up the initial overheat of the water and then stabilize the thermal
fluctuations. Having the a relatively small weight so closely linked
to the flow may be just as effective as having a huge mass in the
group envelope. That would make it an economizing move.
The time line is also telling -- the heavy blocks are later
developments, going with the lighter weight groups, while the early
lever and faema groups (e61 and non-stop) have small blocks and lots
of mass.
The alt.coffee myth, aided by Schomer's writings, is that Italian
espresso design became progressively more mediocre in the 70s and 80s.
I think this is mostly a myth -- I think that the designs and coffees
were economically constrained to be inexpensive, but the sort of "race
to the bottom" we saw in post war US coffee didn't occur. The entries
that Brasilia and NS knocked out in short order for the WBC are a case
in point.
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Date: 30 Mar 2007 21:20:05
From: Jack Denver
Subject: Re: Pressure Profiling Update 3
|
I've always suspected that a lot of what we do here on alt.coffee is
re-inventing the wheel because the Italian manuf. regard all this stuff as
proprietary trade secrets. They've probably ran the same kind of experiments
that some here have done 20 years ago but they're not about to share their
results or the insights they've gained and would look at you as if you were
nuts if you asked.
Then again a lot of them just plain disagree w/ for example a 203F brew
temp - NS would tell you that's way too hot in their view and they aren't
aiming for anything like that. Until I stuck a PID on my Oscar I could
never brew that hot because in order to get to that avg. temp the top of the
pstat cycle was more than the set point of the safety valve. W. PID I can do
it because there is not more than 1 degree of overswing. Then again NS also
believes in ridiculously shallow baskets - maybe their commerical customers
like 12g doubles 'cause they save coffee. I'm betting though that set up at
the factory with the brew temp that they like and the coffee that they like,
they make (very short) coffees that taste just fine - you just have to buy
into the whole philosophy of the brand.
"jim schulman" <jim_schulman@ameritech.net > wrote in message
news:d7br03h4jirojmvqlt4sdd67d2t2uj22ac@4ax.com...
> On Fri, 30 2007 19:17:36 -0400, "Jack Denver"
> <nunuvyer@netscape.net> wrote:
>
>>No, it's not just Elektra - I haven't compared them side by side but the
>>block on my NS is also thicker than it would appear to need to be for its
>>function and judging from the drawing about the same thickness. Could it
>>be
>>that they are purposely taking up space so to get the shower screen down
>>closer to the top of the puck and not leaving headspace which as you said
>>would end up filled with brewed coffee? Or they are adding more thermal
>>mass
>>to the group? There must be some good reason for it because manufacturers
>>are no know for building parts heavier than they need to be.
>
> You could be right. The block on the E61 is small, about the size and
> thickness of a quarter. This does point to thermal management -- on
> lighter weight or non thermosyphom groups, it may be designed to soak
> up the initial overheat of the water and then stabilize the thermal
> fluctuations. Having the a relatively small weight so closely linked
> to the flow may be just as effective as having a huge mass in the
> group envelope. That would make it an economizing move.
>
> The time line is also telling -- the heavy blocks are later
> developments, going with the lighter weight groups, while the early
> lever and faema groups (e61 and non-stop) have small blocks and lots
> of mass.
>
> The alt.coffee myth, aided by Schomer's writings, is that Italian
> espresso design became progressively more mediocre in the 70s and 80s.
> I think this is mostly a myth -- I think that the designs and coffees
> were economically constrained to be inexpensive, but the sort of "race
> to the bottom" we saw in post war US coffee didn't occur. The entries
> that Brasilia and NS knocked out in short order for the WBC are a case
> in point.
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Date: 31 Mar 2007 20:19:30
From: Barry Jarrett
Subject: Re: Pressure Profiling Update 3
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On Fri, 30 2007 21:20:05 -0400, "Jack Denver"
<nunuvyer@netscape.net > wrote:
>it because there is not more than 1 degree of overswing. Then again NS also
>believes in ridiculously shallow baskets - maybe their commerical customers
>like 12g doubles 'cause they save coffee. I'm betting though that set up at
>the factory with the brew temp that they like and the coffee that they like,
>they make (very short) coffees that taste just fine - you just have to buy
>into the whole philosophy of the brand.
perhaps NS machines are better suited for the light roast low dose
scenario.
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Date: 31 Mar 2007 17:44:34
From: Jack Denver
Subject: Re: Pressure Profiling Update 3
|
NS is located in the ches region, slightly north of Rome and on the other
(Adriatic) side of the peninsula, so I would guess that their local style of
coffee would be "northern".
"Barry Jarrett" <barry@rileys-coffee.com > wrote in message
news:6hgt03pjk1jjavgr3mksuhcb8ba2v7d4sd@4ax.com...
> On Fri, 30 2007 21:20:05 -0400, "Jack Denver"
> <nunuvyer@netscape.net> wrote:
>
> >it because there is not more than 1 degree of overswing. Then again NS
> >also
> >believes in ridiculously shallow baskets - maybe their commerical
> >customers
> >like 12g doubles 'cause they save coffee. I'm betting though that set up
> >at
> >the factory with the brew temp that they like and the coffee that they
> >like,
> >they make (very short) coffees that taste just fine - you just have to
> >buy
> >into the whole philosophy of the brand.
>
>
> perhaps NS machines are better suited for the light roast low dose
> scenario.
>
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Date: 29 Mar 2007 18:22:49
From: gscace
Subject: Re: Pressure Profiling Update 3
|
On 29, 5:08 pm, "Ken Fox"
<morceaudemerdeThisMerdeG...@hotmail.com > wrote:
> "gscace" <gregory.sc...@nist.gov> wrote in message
>
> news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
> Pressure Profiling Update 3
>
> >>>I think I'm homing in on some concrete information about pressure
> >>>profiling that is worth blabbing on about, so here goes:
>
> Hi Greg,
>
> This is all very interesting. I am wondering, however, to what extent your
> observations might be dose-dependent.
>
> In shot timing, the dosing of the basket (in my experience) trumps the other
> factors such as grind and tamping. Therefore, your observations might be
> valid for your style of dosing and not transferable (or requiring
> modification) for other dose levels. In addition, there might be interplay
> with your grinder type, e.g. planar vs. conical vs. mixed (DRM).
>
> What kind of baskets are you using and how much coffee are you putting into
> them? Which grinder?
>
> ken
Grinder is a Robur. Burrs are conical. With the Ethiopians I'm using
a straight sided LM ridgeless double that's not particularly updosed.
Dose is 18 g. The Toscano from Counterculture was updosed pretty hard
by Nick in the same basket. The Terroir SO Brazil was best when 13 to
13.5 g was dosed into a shallow Rancilio double. This was the
suggestion by Peter, and was born out by my experience as well in
subsequent days, although one side benefit of the pressure profiling
was that getting rid of the bitter taste from the dilution stage of
the extraction allowed one to experiment with updosing a little and I
tried using the ridgeless LM basket with it. The result was improved
mouthfeel at the expense of a little clarity in taste. The sweet
nuttiness was so interesting and our of my normal lexicon that i went
back to 13.5 g doses just to get the shot clarity.
For Nick's tests, Nick was the espresso machine driver. His dosing
mechanics are pretty good. For the Terroir stuff, Peter pulled the
shots and we weighed all doses, which pretty much knocked out dosing
inconsistency as a source of variability. In the case of the Terroir,
the difference in taste from profiling was not subtle.
-Greg
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Date: 29 Mar 2007 17:42:42
From: Travesso
Subject: Re: Pressure Profiling Update 3
|
I tested my portable espresso machine -- http://travesso.com/index-4.html
-- with Nick. He thought that it was possible that the reason our
simple little 4" unit was making such good espresso with a POD was
that we had complete control over the pressure curve. We have
complete control over the pressure curve, up or down, over the entire
brew time.
We did not show him the ground coffee version, but I really like
having full control over the pressure.
As a side, I think the Illy book states that at over 150PSI the coffee
stabilizes itself. I have found that to be somewhat true. From a PSI
of 180 to 250 (I went all the way to 1200PSI) I did not find a real
difference. Please note, that all water stopped when I did this with
ground coffee.
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Date: 29 Mar 2007 19:08:57
From: Jack Denver
Subject: Re: Pressure Profiling Update 3
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A couple of thoughts:
1. I wonder how your profile compares to a spring lever machine where there
is also an intitial hump and then a taper?
2. I also wonder whether, once you determine an optimum profile, whether it
would be possible to implement it without fancy electronics - for example a
relief valve with a motor driven cam (turning at 2 rpm) in the shape of the
profile pressing against the relief spring?
"gscace" <gregory.scace@nist.gov > wrote in message
news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
Pressure Profiling Update 3
I think I'm homing in on some concrete information about pressure
profiling that is worth blabbing on about, so here goes:
The most successful general profile that I have come up with to date
(I've now got an excel file with a bazillion profiles mapped out in
it) is a pressure profile in which the pressure rapidly increases from
some nominal start value to 9 bars at the group (elapsed time of 1
second from start to full pressure) with a short 9 bar soak, then
ramps downward in a slow linear fashion (straight line degradation) to
around 7 ½ bar, with a more rapid, second-order (curved downward)
slope over the last few seconds to around 6 bar, arriving at 6 bar 30
seconds after initiation of the brew cycle. This general shape can be
used with or without a pre-infusion step. The pre-infusion that I've
been using is to soak the cake at around 2 - 3 bar for 3 seconds, then
quickly ramping to maximum value with an exponentially increasing
slope. Full pressure is attained 3 seconds after the end of the low-
pressure soak. This combination produces liquid evenly over the
bottom of the filter basket almost as soon as the pressure begins its
rapid increase. Regardless of whether or not pre-infusion is used,
I've been using a very similar profile toward the end of the brewing
period. If pre-infusion is not used, I increase the time of the high-
pressure soak by a few seconds.
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Date: 29 Mar 2007 16:08:19
From: Ken Fox
Subject: Re: Pressure Profiling Update 3
|
"gscace" <gregory.scace@nist.gov > wrote in message
news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
Pressure Profiling Update 3
>>>I think I'm homing in on some concrete information about pressure
>>>profiling that is worth blabbing on about, so here goes:
Hi Greg,
This is all very interesting. I am wondering, however, to what extent your
observations might be dose-dependent.
In shot timing, the dosing of the basket (in my experience) trumps the other
factors such as grind and tamping. Therefore, your observations might be
valid for your style of dosing and not transferable (or requiring
modification) for other dose levels. In addition, there might be interplay
with your grinder type, e.g. planar vs. conical vs. mixed (DRM).
What kind of baskets are you using and how much coffee are you putting into
them? Which grinder?
ken
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Date: 31 Mar 2007 01:08:31
From: Ed Needham
Subject: Re: Pressure Profiling Update 3
|
Or even temperature dependent. Pressure, dose, temperature, grind...
A number of variations need to be quantified before jumping to conclusions.
Greg's tests add to the database for sure.
Thanks
--
*********************
Ed Needham®
"to absurdity and beyond!"
http://www.homeroaster.com
(include [FRIEND] in subject line to get through my SPAM filters)
*********************
"Ken Fox" wrote in message news:572rmaF2bae2kU1@mid.individual.net...
> "gscace" wrote in message
> news:1175204989.286896.22860@n76g2000hsh.googlegroups.com...
> Pressure Profiling Update 3
>>>>I think I'm homing in on some concrete information about pressure
>>>>profiling that is worth blabbing on about, so here goes:
> This is all very interesting. I am wondering, however, to what extent
> your observations might be dose-dependent.
>
> In shot timing, the dosing of the basket (in my experience) trumps the
> other factors such as grind and tamping. Therefore, your observations
> might be valid for your style of dosing and not transferable (or requiring
> modification) for other dose levels. In addition, there might be
> interplay with your grinder type, e.g. planar vs. conical vs. mixed (DRM).
>
> What kind of baskets are you using and how much coffee are you putting
> into them? Which grinder?
>
> ken
>
>
>
>
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