And now that I’ve finally read the Novotný article in Zymurgy (reply #9) I don’t even feel like busting out the hydrometers to cross check the refractometer, the evidence behind the calculations looks solid. I might just go all-in on the refracto. I much prefer working in Plato anyway (right, Jim?) I love how just about every brew cycle the forum has me getting out of some rut I was stuck in and making some unexpected improvement!
Why is that? Just the high level overview if you don’t mind. I’m curious.
I’ve had such good luck with Sean’s calculator.
Big Monk, have a look at the Novotný article, Jul/Aug 2017 Zymurgy (and the graph in the original post.) OP’s calc allows use of Novotný equation, which tracks hydro closer than Terill, and he also has really good empirical data behind the calculations it includes for fermenting and fermented beer.
I’m good with that, I’m just curious about Dave’s statement where he says it tracks the “Old Cubic” from ST’s calculator. Plugging in some data and expanding ST’s sheet to include columns for apparent Attenuation for the “Old Cubic” column shows me getting unrealistic amounts of Attenuation.
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I don’t know from “old cubic.” But looking at the article and the evidence presented, like I said above, I’m ready to shelve the hydros and use the OP’s calculator. You will understand the material better than I, but the article references foundational research you might even be able to incorporate on your own. He just did the actual tests to confirm the corrections for fermenting/fermented beer. Now I don’t have to, and I suspect Dave has already tested it out himself and doesn’t need me to!
To use the calculator you just have to register with their website, a Prague-based homebrew group.
I registered earlier today and ran some brewery numbers from about 10 WY3787 batches and the OP calc had my attenuation outside the realm of reality. I’m going to locate the article and give it a read to make sure I’m not missing anything.
I have only ONE data point to offer at this point: the beer I have on tap right now. I stole a drop or two and put it through the OP’s calc. The Terill result is indeed closer to my notes than the Novotný, both are a little lower. But my notes are of a hydro reading of beer from the lagering tank, with some suspended yeast and upwelling of CO2, so I’m inclined to trust either of the refracto numbers over my hydro as noted, they are right in the expected range of attenuation (78-80% with 34/70) whereas I wondered why I was only showing 76%. Which to trust more? I’ll wait for somebody smarter to chime in. They both look highly plausible, and FG is far less critical than mash and boil data. Either should be close enough for judging time for a diacetyl rest. Awaiting further information. I’m going to go drink the rest of this glass of Pils, thank you. 8)
I’m trying to get my hands on the zymurgy article so I can look at the write up. Then I’ll take some notes over the next few batches.
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Let me guess, you’re not an AHA member? If you are it’s easy to access from the main site. And as an aside, remember the kerfuffle over that keg purging disinformation? Well it’s nice to see the level of material being published with Gordon Strong as technical editor!
I read the Zymurgy article, and there is an equation listed in it. I put that into my spreadsheet right next to Terril’s old cubic that I had been using. For my current batch, the Novotny formula gave values about 2 points higher down to a gravity of 1.032, then 1 point higher below that. At the end of fermentation the ST formula gives 1.008, the Novotny formula gives 1.009 and my hydrometer gives 1.009. I would say that these are all so close to each other that it is hard to really say that one is better than the other. I need lots more brews to be sure, not that I needed any extra motivation to brew.
See earlier post:
https://www.homebrewersassociation.org/forum/index.php?topic=28544.msg404356#msg404356
Terrill’s research was only for “well fermented beer”. Novotny’s works very accurately at ANY point during fermentation… and more accurate at FG in my experience as well.
Old Cubic is almost just as accurate in my own experience. YMMV.
Thanks Dave. That helps me line up a few mental data points. I have for reasons irrelevant here taken my last hydro reading differently in the last few batches. Novotný, if correct, would in this instance confirm I’ve had no actual change in attenuation. Score one for refracto.
Awesome. I put together a modified ST sheet for tracking and Bryan and I are going to take some notes over the course of 20 or so batches.
I placed this EDIT above, but here it is again because it matters:
FYI, I add a constant 0.001 to every result when using the Old Cubic. A little tweak like that can make a real difference in our judgment of it. The curvature is not affected, just the vertical placement on the graph.
My observation, when taking into consideration that I am interested only in final gravity and last 4 points preceding it (for accurately transferring beer with extract to packaging), is that most of the graphs converge at or near final gravity. The issue with that then is that if the Old Cubic and Novotny equations estimate a lower FG with a constant input (Original Bx), it would jive with some of the numbers I have now, i.e. unrealistic attenuation based on empirical findings.
I’ll have to track this over some batches and see what happens.
FYI: You can also determine Refractometer Correction Factor online here: HomeBrewMap - Refractometer Correction Factor
Yeast suspension effect posted in a new thread under general topics
Trusting Novotný enough that I’m doing current batch without bothering with hydrometers. Just checked mid fermentation, and OP’s calculator with Novotný shows gravity exactly where it always is at this point with this beer.
Awesome
I added the novotny equations to the Terrill sheet and will be tracking from now on. I have a suspicion that the Terrill equations are more accurate at higher levels of attenuation.