WBC Procedure for Measurement of Brewing Water Temperature - Page 4

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barry

#31: Post by barry » Nov 18, 2005, 8:44 pm

another_jim wrote:However, if I were an HX manufacturer, I'd reject it and refuse to submit my machines to this test. They could justly claim that the inter-shot procedure is systematically biased in favor of dual boilers.
as one of the folks who spent a lot of time on the phone in deep discussions about the development of the protocol, i'll throw in my $.02:

the protocol isn't biased for or against any machine or machine system. the objective presented for machine performance was stable, repeatable brew temperatures over a variety of duty cycles. the protocol reflects that objective. we knew the HX people might have kittens over this, and really went out of our way to make sure the protocol fairly measured machine performance. we also knew that the protocol would show the cold start of marzoccos. the duty cycle variation was specifically intended to show weaknesses in machine performance, for both types of machines. note the wbc/usbc competition schedule has a variable duty cycle: the competitor can use it as much as they like during setup, and then the machine sits for a few minutes (an unknowable period), and then it is put back in service at an unknowable duty cycle.

No matter what the HX design, the equilibrium shot temperature will depend on the shot making pace. If the pace is slow, the temperature over a long series will settle at a higher level than if the pace is fast. This has to be, since at the slower pace, the HX is heating up more. You are dumping the first four very slow measures for inter-shot calculations. But you still have the pace accelerating from 2 min 35 seconds to 45 seconds between shots. This will always cause the brew temperatures to drop for the later shots.
recall that it was precisely this phenomena which pushed me down the path of machine modification, and recall that the manufacturer denied any such problem existed.

The easiest, and I think correct, fix is to allow each manufacturer to specify the amount for the preshot flushes.
an easy fix, no doubt, except that no manufacturer specifies that any such flush is required during the routine operation of their machines. this harks back to coffeegeek's test procedure, which only follows "out of the box" performance, not how the machine performs after tweaks and surfs and other machinations which are not specified by the manufacturer in the operating instructions. if the manufacturers want to stand up and say, "yeah, our machines are only stable if you do x, y, and z," then x, y, and z may become part of the protocol.

in essence, you're suggesting the hx manufacturers be allowed a self-determined handicap because their machines won't perform even up to their own specifications and marketing. how about getting the manufacturers to make machines which will perform up to the desired specs? the goal was to find out how machines really perform, not how they perform after the barista spends ten years becoming intimate with the quirks and foibles of the machine. yeah, i can start my MGB w/o any problem, but valet attendants invariably cannot (it's that manual choke thing).

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barry

#32: Post by barry » Nov 18, 2005, 8:50 pm

another_jim wrote:The test does not reflect WBC use, which is to pull 3 shots at each group at roughly around 2, 5, and 9 minutes into the presentation, with the final two rounds having looser requirements from the taste point of view since they are being used as the base for other drinks.

i can't recall seeing that dynamic with any regularity (or even at all). maybe that's the ideal dynamic, but reality is much much different. i've even watched people just use one group for the whole competition.

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another_jim
Team HB

#33: Post by another_jim » Nov 18, 2005, 11:26 pm

barry wrote:in essence, you're suggesting the hx manufacturers be allowed a self-determined handicap because their machines won't perform even up to their own specifications and marketing. how about getting the manufacturers to make machines which will perform up to the desired specs? the goal was to find out how machines really perform, not how they perform after the barista spends ten years becoming intimate with the quirks and foibles of the machine. yeah, i can start my MGB w/o any problem, but valet attendants invariably cannot (it's that manual choke thing).
I'm still not getting this. I'm suggesting that specifying a flush of two seconds is arbitrary and unrelated to to the functionality of the test. Since it is arbitrary, you'll get questions of "why 2 seconds". Your answer is "for consistency." So why not 3 seconds or 8 or whatever. And why be consistent in this regard? It's unrelated to what is being tested, so it's like specifying how high the machine should be. If a manufacturer wants some other timing, I don't get how it would in any way affect the procedure.

You may be right, manufacturers may be so arrogant that they'll say their machines can violate the laws of thermodynamics. But I suspect this is more the department of the sales reps; and the manufacturers wanting to underwrite the WBC (they'll be lining up when it catches on more) will take a close look at the entry requirements.

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barry

#34: Post by barry » Nov 19, 2005, 12:01 am

another_jim wrote:I'm still not getting this. I'm suggesting that specifying a flush of two seconds is arbitrary and unrelated to to the functionality of the test. Since it is arbitrary, you'll get questions of "why 2 seconds". Your answer is "for consistency." So why not 3 seconds or 8 or whatever. And why be consistent in this regard? It's unrelated to what is being tested, so it's like specifying how high the machine should be. If a manufacturer wants some other timing, I don't get how it would in any way affect the procedure.
as i mentioned on a.c, yes, there is some arbitrariness in the "2 seconds". we had to have a time for the wbc required screen flush. one second seemed too difficult to handle during testing, three seconds seemed too long (and might have an influence on the thermal performance), and we didn't think we could get away with saying "blip the pump". this is not a thermal flush; this is a screen flush only. it has nothing to do with marzoccos. it has nothing to do with heat exchangers. no manufacturers currently specify a flush of any sort, so you're creating issues that aren't there.

and yeah, we spent a lot of time discussing this sort of stuff.

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malachi

#35: Post by malachi » Nov 19, 2005, 5:39 pm

To be clear - this is not a temp-related flush but rather a cleanliness-related flush?
"Taste is the only morality." -- John Ruskin

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barry

#36: Post by barry » replying to malachi » Nov 19, 2005, 6:11 pm

iirc, that was my understanding from our discussions last winter. i've reread what was published here and it says "to simulate a temperature equalization flush" in section 5.2(B), which does not appear in my draft copy from last winter. my comment notes to greg talk about how my experience has been that flushes after the portafilter is removed tend to be screen cleaning flushes and those before the portafilter is reinserted tend to be thermal flushes, so perhaps there was a misunderstanding between us on the roll of the reinsert flush. iirc, those comments had more to do with whether two flushes were needed at all, and i think further phone conversations included a discussion of the wbc rules allowing screen cleaning flushes either before or after, just so long as it happened somewhere, and that we decided on two flushes to account for the before and after, since the rules aren't clear. i'm almost positive the 2 seconds was determined as a comfortable compromise between the too-short 1 second and the too-long 3 seconds (in reference to a screen cleaning flush). i would like to hear from greg about what his notes say, cuz i really can't see him agreeing that 2 seconds could be considered a useful simulation of any sort of temperature related flush.

of course, my memory might be whacked, in which case i apologize in advance. ;)

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malachi

#37: Post by malachi » Nov 19, 2005, 6:15 pm

If simulating cafe situations, then it would indeed be to mimic a cleaning flush (given the published description). That "pulse flush" is best practices in cafes and is, as noted, designed for cleanliness purposes rather than temp purposes.
"Taste is the only morality." -- John Ruskin

gscace

#38: Post by gscace » Nov 19, 2005, 11:37 pm

barry wrote:
iirc, that was my understanding from our discussions last winter. i've reread what was published here and it says "to simulate a temperature equalization flush" in section 5.2(B), which does not appear in my draft copy from last winter. my comment notes to greg talk about how my experience has been that flushes after the portafilter is removed tend to be screen cleaning flushes and those before the portafilter is reinserted tend to be thermal flushes, so perhaps there was a misunderstanding between us on the roll of the reinsert flush. iirc, those comments had more to do with whether two flushes were needed at all, and i think further phone conversations included a discussion of the wbc rules allowing screen cleaning flushes either before or after, just so long as it happened somewhere, and that we decided on two flushes to account for the before and after, since the rules aren't clear. i'm almost positive the 2 seconds was determined as a comfortable compromise between the too-short 1 second and the too-long 3 seconds (in reference to a screen cleaning flush). i would like to hear from greg about what his notes say, cuz i really can't see him agreeing that 2 seconds could be considered a useful simulation of any sort of temperature related flush.

of course, my memory might be whacked, in which case i apologize in advance. ;)
You're right. I recall the discussions and it's bad writing on my part.

-Greg

wogaut

#39: Post by wogaut » Dec 05, 2005, 5:00 pm

Hi Greg,

I really welcome finally having a standardized test procedure, that hopefully most people will use!

A question about the idle time between shots:

the first idle time is shown as 10 minutes. Is that before or after the first shot of the 14 repeats?
If it's before, I'm confused since you write about having the machine get to equilibrium for an hour or so (after backflushing?) and then having it sit idle for another 10 minutes doesn't do anything.

I was looking at your graph in the GS3 temperature thread, and it looks as if the first shot occurs after 10 minutes.

Your clarifications are highly appreciated!

Wolfgang

gscace

#40: Post by gscace » replying to wogaut » Dec 07, 2005, 5:35 pm

The first idle time is before the first measurement. We felt that while we specified that the portafilter and thermometer were to remain in the group, and that the machine was to be hot for an hour, we hadn't adequately prevented anyone from flushing or otherwise dicking around immediately before getting the first measurement, so we specified that you had to wait the 10 minutes before making the first measurement. That makes it really clear.

-Greg