www.baratza.com: skilled in the art of grinding

WBC Procedure for Measurement of Brewing Water Temperature - Page 3

Postby gscace on Mon Nov 14, 2005 3:11 pm

cinergi wrote:[quote="malachi"]That's not what Schomer used - it's not what was used to create most if not all of the profiles you're talking about.
The Scace has been around for what... 3 months?


The shape of a profile using the Scace device is very similar to the profiles you get when placing a t/c inside the cake. In other words, you see the same sharp increases in temp during the 1st 8 - 10 sec. resulting in one shot stability readings of +-3 degrees if you just throw out the 1st 3 sec. whereas, throwing out the 1st 8 - 10 sec. results in much lower stability readings of +-.5 degrees.[/quote]

Again, why would you want to throw out ramp up data that must have an effect on the cup. We should be examining all of the data that is reasonable, not just the pretty stuff. Usually the ugly stuff is more interesting anyway.

-Greg
gscace
Team HB
 
Posts: 627
Joined: Aug 12, 2005
Location: Laytonsville MD
Quotable Quote
"There are no short cuts to becoming a highly skilled barista. You need to pull and taste lots of shots. You need to X. You need to Y. You need to... Why do I keep saying "need"? Because you can't access what high-end equipment does better without these skills." --Russel, Should I feel guilty about buying a La Marzocco GS/3?


Postby gscace on Mon Nov 14, 2005 3:16 pm

cinergi wrote:I'm just trying to figure out how someone like Schomer and others can say their machines are stable to within .5F - 1F. It seems the only way anyone can make this claim is to ignore the 1st 10 readings. If you only ignore the 1st 3 readings, there is no way to get any lower than 5F - 6F variance within a shot (i.e. max temp - min temp ignoring 1st 3 readings).

Doug


It's actually pretty clear how they can do it. They set up groundrules that allow them to do so. According to your post, Schomer bases his data on the last 15 seconds of the 25 second shot. We decided to include all data except that data produced by a thermometer that is substantially not in agreement with the actual temperature because of response time issues. We did this because this data is relevant in our opinion. Note that David Schomer is not an author of the standard.

-Greg
gscace
Team HB
 
Posts: 627
Joined: Aug 12, 2005
Location: Laytonsville MD

Postby gscace on Mon Nov 14, 2005 3:19 pm

cinergi wrote:Can anyone give me just one example of any machine that has a intrashot variance (max temp minus lowest temp ignoring readings 1 - 3) of less than 5F (as tested according to WBC testing procedures)?


Certainly my LM Linea is better than 5 degrees. Data I have was collected using a datalogger, and the data was reduced according to the standard.

-Greg
gscace
Team HB
 
Posts: 627
Joined: Aug 12, 2005
Location: Laytonsville MD

Postby gscace on Mon Nov 14, 2005 3:46 pm

cinergi wrote:On the 2 machines that I have tested (both dual boiler rotary pump models) the 1st reading always seems to be somewhere between 180 -185 while the 4th reading seems to be between 195 - 198 on a consistent basis. That being the case it would seem the "one shot stability" rating is highly dependent upon the machine's set point. Set points near 198 will have very small intra shot variances while set points like 203.5 will have large variances. This leads me to conclude that as it is currently defined and measured "one shot stability" seems meaningless.


As I emailed you, and as is described in the technical rationale for the standard, the first 3 seconds are not used because the answer reported by the thermometer is not the same as the actual temperature, for reasons described in the standard. Beyond that, the stability data is real stability data. The temperature rampup is certainly reasonable to look at. Rampup rate can be influenced by how hot the dispersion block and screen are, the group temperature relative to the water temperatue, and other factors specific to the machine. So it is not meaningless at all, particularly since these relatively cold or hot parts influence the temperature of water hitting the coffee. It's important to remember that what we are trying to measure is the temperature of the water that hits the coffee, period. Artificial boundaries limiting the data used, such as "it's not as stable as the temperature later in the shot" should not influence the data.

Have you made measurements at 198 degrees setpoint temperature, and 203.5 degrees setpoint temperature to see what the influence of setpoint will be? I would be interested in your results. I think the ones you sent me were for only 201 degrees. I would suspect that temperature setpoint may have some influence in the stability value, but conceptually that doesn't bother me much. If you notice, the WBC standard prescribes a uniform measurement and data reduction method only. It doesn't specify the groundrules for acceptance / rejection, or tell you at which setpoint temperature you have to do this stuff at. It can't because it has to be somewhat flexible wrt brewing temperature setpoint to suit coffees that may be used for a competition. If stability values change due to changes in setpoint, then that may be useful information for someone who is designing a machine or evaluating one for use. The folks selecting a machine for use in competitions may end up making a decision partially based on uniformity of stability results over a variety of brewing temperatures, and we don't want to limit them by the standard. Again, we want good, technically sound data without preconceptions.


-Greg
gscace
Team HB
 
Posts: 627
Joined: Aug 12, 2005
Location: Laytonsville MD

Postby gscace on Mon Nov 14, 2005 3:54 pm

cinergi wrote:well, if you take the scace thermofilter out for 15 sec. then do a 2 sec. flush then put the p/f back in and start the shot I don't see how to get the 4th second up to the set point especially if the setpoint is high like 204. Seems like most machine profiles start out at somewhere in the 180-190 range and that greatly depends on how fast you are getting the p/f back in.


Doug:

One of the things we strived to do in writing the WBC standard was to get the data with as little outside interference as possible. So we standardized a couple of things that are used across the board by reasonable baristas - the group cleansing flush after brewing, for instance. Other than that, we ignore things that mask results, like heating / cooling flushes. In our opinion, the holy grail is a machine that produces the same average brew temp every time, with the same stability profile every time it is used. By removing artificial practices that cover up machine deficiencies, we can see how well machines measure up to our ideal. In practice one does not use a machine in the way that we test them. We cool or heat groups. We warm dispersion blocks.

-Greg
gscace
Team HB
 
Posts: 627
Joined: Aug 12, 2005
Location: Laytonsville MD

Postby another_jim on Fri Nov 18, 2005 5:38 am

I've been thinking about the nitty-gritty of this standard for a while. It has the advantage of being precise, reproducible, simulating varying traffic conditions very well, and encompassing intra and intershot stability with a single statistic for each. 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.

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. (Potentially, they could avoid this with a very large HX, and a too high boiler pressure, so the temperature would rise at a steady pace and be offset by the accelerating shot pace -- but this an even more perverse result, since they would be deliberately mis-setting the machines to show well under this procedure)

The easiest, and I think correct, fix is to allow each manufacturer to specify the amount for the preshot flushes. For instance, Brasilia might specify 6 ounce flushes for the early shots, down to 2 ounces for the shots at 1 to 2 minute intervals, and down to no flush at all for the final 45 second interval shots. If they don't make a specification on this, stick with the existing one. This would be fair to their claim that the machines are stable under different operating conditions given skilled and trained baristas, and would still allow for the two test statistics to be comparable between machine brands. You are still forcing each manufacturer to test the machine in variable traffic conditions, but simply allowing them to specify, in more detail, how their machines are to be operated.

And if one of them sticks a TC in the grouphead, puts on a readout, and specifies a flush to X degrees, more power to them -- provided that the model is part of their regular commercial line, not a wbc one-off.
User avatar
another_jim
Team HB
 
Posts: 9161
Joined: May 05, 2005
Location: Chicago

Postby malachi on Fri Nov 18, 2005 12:56 pm

I understand how this would seem to bias against HX machines, but the reality is that this is all designed for evaluating machines for the WBC - and for the WBC it's unrealistic to have machines that require some specific and varying flush methodology.
"Taste is the only morality." -- John Ruskin
malachi
 
Posts: 2544
Joined: May 05, 2005
Location: sfca

Postby another_jim on Fri Nov 18, 2005 4:08 pm

malachi wrote:I understand how this would seem to bias against HX machines, but the reality is that this is all designed for evaluating machines for the WBC - and for the WBC it's unrealistic to have machines that require some specific and varying flush methodology.


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. Moreover, if an HX machine is used, you'd want to know how much to flush it for those intervals, and especially for the initial espresso shot. Presumably, the test data would be available, and you could use it as you please.

Suppose someone does submit an HX machine with a grouphead sensor, and the user instruction is to flush until the sensor reads, say 0.5C higher than the desired shot temperature. If you then insist on the flush amounts in the protocol as written, the manufacturer would say you are in effect disabling the final temperature control. Now suppose he resubmits it with the sensor hooked to the autodosing, so the machine flushes automatically to a set temperature, and won't run with the PF mounted till it's there. Do you disqualify the machine entirely? No matter how you answer these questions, the fixed flush part of the standard looks more and more absurd.

Let me be completely blunt here. You can stick with this standard and LM as the sole supplier; and everyone will be happy. But I cannot see any HX manufacturer agreeing to it; and I cannot see it as a good faith step for creating an open competition for manufacturers:

1) The measuring protocol in effect prescribes how the machines are to be operated.
2) One of the co-authors is Bill Crossland of LM.
3) The operating instructions closely follow good barista practice on LMs and only on LMs.

I used to work for a company that bid on process and HVAC control jobs. We called specs like this proprietary, and assumed it was ghost-written by the favored company. We loved it when we were doing the ghost writing; and made a big stink when it was another one. In the end, unless the fix came from upper management, the engineer in charge of writing the spec usually ended up fired.
User avatar
another_jim
Team HB
 
Posts: 9161
Joined: May 05, 2005
Location: Chicago

Postby gscace on Fri Nov 18, 2005 6:09 pm

another_jim wrote:[quote="malachi"]I understand how this would seem to bias against HX machines, but the reality is that this is all designed for evaluating machines for the WBC - and for the WBC it's unrealistic to have machines that require some specific and varying flush methodology.


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. Moreover, if an HX machine is used, you'd want to know how much to flush it for those intervals, and especially for the initial espresso shot. Presumably, the test data would be available, and you could use it as you please.

Suppose someone does submit an HX machine with a grouphead sensor, and the user instruction is to flush until the sensor reads, say 0.5C higher than the desired shot temperature. If you then insist on the flush amounts in the protocol as written, the manufacturer would say you are in effect disabling the final temperature control. Now suppose he resubmits it with the sensor hooked to the autodosing, so the machine flushes automatically to a set temperature, and won't run with the PF mounted till it's there. Do you disqualify the machine entirely? No matter how you answer these questions, the fixed flush part of the standard looks more and more absurd.

Let me be completely blunt here. You can stick with this standard and LM as the sole supplier; and everyone will be happy. But I cannot see any HX manufacturer agreeing to it; and I cannot see it as a good faith step for creating an open competition for manufacturers:

1) The measuring protocol in effect prescribes how the machines are to be operated.
2) One of the co-authors is Bill Crossland of LM.
3) The operating instructions closely follow good barista practice on LMs and only on LMs.

I used to work for a company that bid on process and HVAC control jobs. We called specs like this proprietary, and assumed it was ghost-written by the favored company. We loved it when we were doing the ghost writing; and made a big stink when it was another one. In the end, unless the fix came from upper management, the engineer in charge of writing the spec usually ended up fired.[/quote]

Actually Jim, we had philosophical reasons for writing it this way. We think that the ideal machine would exhibit the same thermal performance off idle compared to full-tilt boogie. We think it's reasonable to write the standard in a way that allows us to examine off idle performance without flushing. It's not fair to force competitors to play on something that doesn't require specialized experience with the machine to begin with unless everyone gets lots of time on the machine. Why does art of running an inferior machine trump the art of the coffee? The machine for next year was selected partially on that basis. Currently, no manufacturer of hx machines installs flushing thermometry in its machines, so it's a moot point for now. Currently there is no good information re flushing specific machines. Are you suggesting that this get turned into more of a research project than it already is? IF a machine manufacturer doesn't like the results after the tester performed the manufacturer's flushing ritual, are there then going to be claims of "you didn't do it right"? From our perspective it's just better to do it as we wrote.

I disagree that the deck is stacked by the authors. The authors of the standard are reasonable people to do the job. I work in applied thermometry. John Sanders is head of the WBC technical standards committee. Barry Jarrett is very capable, understands instrumentation and has experience with a wide variety of machinery. Bill is a good mechanical engineer with wide experience who agreed to help work on this. From my perspective, his working for LM doesn't mean squat wrt this standard. He knows a lot about coffee machines in general. In our view, and in our experience so far, the measurement method does expose the warts of various machinery. Our work is also supported by the other members of the technical standards committee, who adopted the standard.

Your item 3 is just plain incorrect. If you perform this measurement procedure on a LM Linea you will learn that this procedure is not good barista practice on that machine as well. However, the procedure shows what the weaknesses of the Linea are, gives you a clue about what to do to compensate and also gives you good information about the ultimate capability of the Linea.

You should know that one heat exchanger machine submitted to the WBC had extremely good reproducibility over all duty cycles, when measured using this method. In fact, it had the best reproducibility of all machines submitted. It was not selected for other reasons.

Jim, have you made some measurements of machinery using this method? If so, I'd love to see your results. If you have extensive experience with the machine, does the measurement procedure give you information about how to use the machine that reflect your experience?

-Greg
gscace
Team HB
 
Posts: 627
Joined: Aug 12, 2005
Location: Laytonsville MD

Postby another_jim on Fri Nov 18, 2005 7:40 pm

gscace wrote:Jim, have you made some measurements of machinery using this method? If so, I'd love to see your results. If you have extensive experience with the machine, does the measurement procedure give you information about how to use the machine that reflect your experience?

-Greg


Fair enough. I don't have the Scace device, but I do have Schomer baskets. I'll use those to run tests on the Tea and maybe the Peppina, if I can rig the otherwise useless single basket with a TC and microconnector that will go through the trousered PF. I'll follow your protocol first. Then I'll play manufacturer, research a bit, and follow the same protocol, substituting an equilibration flush of X seconds for the 2 seconds (just one time, e.g. 3.5 seconds, not a different one for each round -- I appreciate that this would be a pita, and also not prove much, since one cannot really start a timer at shot end, consult a table, etc etc). I don't have a logging recorder, but will take readings every 2 seconds to 0.1C resolution (I'll preprint a form so I just need to dot the number, rather than write it down, and get some practice with dry runs).

The Schomer basket is buffered compared to the Scace device, so the under temp early in the shot will be worse, and the stability later better. That means the results won't be comparable to yours. However, the alternative flushes should be comparable.

Given the construction of the Peppina, it may blow away everything you've tried so far :wink:

I'll post all the data, and various ways of describing it, and then report back here. I have a busy weekend, so this will probably happen Monday.
User avatar
another_jim
Team HB
 
Posts: 9161
Joined: May 05, 2005
Location: Chicago