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 Home Brew Forums > Ray Daniels / Zymurgy Alternate ABV formula
06-30-2014, 08:32 PM   #1
afr0byte
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 Ray Daniels / Zymurgy Alternate ABV formula

Hey, does anyone happen to know if the alternate formula as described here: http://www.brewersfriend.com/2011/06...lator-updated/ is actually more accurate for estimating the ABV of high gravity beers? I'm curious since I happen to have a barleywine fermenting at the moment.

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06-30-2014, 08:45 PM   #2
Hermit
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Interesting. I've done a lot of reading but don't remember seeing that. Beer making is an industry that is hundreds of years old and it is sometimes hard to separate out mythology that has become 'fact' and reality. To paraphrase Twain, "Fact is a lie repeated.

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06-30-2014, 09:11 PM   #3
ajdelange
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I have always used the simple formula ABW = f(OG)*(OG - AE) where OG and AE are in °P and f is a number near 0.421 which depends on the OG. There is a simple formula for f(OG) in Section 4.5.4 of the monograph at http://wetnewf.org/pdfs/Brewing_arti...ar_Gravity.pdf. It is derived from numbers attributable to Balling and as given by DeClerck. Note that the formula yields value in ABW which must be converted to ABV by multiplying by the SG of the beer and dividing by the SG of pure ethanol.

How accurate is this? Can't say. I always check OG and, of course, AE and nearly always measure the ABV and TE. From these one can back calculate OG. I've never had close agreement (let's say 0.5 °P discrepancy is typical. But then what is the OG really? How do we account for things like water lost to evaporation (scrubbed out by the CO2) and dilution by the starter (and even the alcohol and extract contributed by the starter). What about errors in hydrometer readings of OG?

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