Refractometer alcohol correction question

[mthhurley]

I use a refrac to measure everything and I've been using a spreadsheet that Morebeer.com publishes that corrects the FG for the alcohol content. However I was also just screwing around with the calculator in Promash and I got dramatically different results.

OG 12.5 plato
FG 6 plato

Using the MoreBeer Sheet http://morebeer.com/learn_vids/vids_refract, it says I'm at 1.009 and therefore 5.4% ABV

However using the %Alc calculator in ProMash, I put 12.5 as the OG, 6 as the FG and it tells me that my FG is 1.024 so ABV 3.6%.

What am I doing wrong and which is correct?

[andy77]

Promash doesn't make the after fermentation correction for the refractometer, it's treating that number like you're reading it off a hydrometer. The Morebeer sheet is correct, and it's what I use.

[Steelers&Beer]

+10000000000000000 to andy77!

[ZZ]

Take a hydrometer reading and see which number is closer.

[mthhurley]

Thanks all. I read elsewhere that ProMash made the correction. So I'll stick to the spreadsheet.

[Maarten]

You might want to have a look at this site:

http://seanterrill.com/2010/07/20/towar ... rrelation/

[ajdelange]

My recollection is that ProMash lets you dial in a correction factor. OTOH I tried the MoreBeer calculator on the limited data set I have (7 beers) and found it generally pretty good. The worst error was about 1 °P.

[TheDarkSide]

I've been using Beersmith to do these calculations for me. Anyone know how accurate they are?

Either way, I haven't been disappointed in the beer.