Post-carb ABV? - Home Brew Forums

 Home Brew Forums > Post-carb ABV?

02-07-2013, 02:24 AM   #1
codyjack
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Jan 2013
Posts: 17
Liked 2 Times on 1 Posts

I was wondering if there is a way to find ABV after carbonation. I know the calculation for finding it post-fermentation, but I want to know my alcohol content after the priming sugar is converted. I would imagine the carb would throw off any gravity readings, so how is this accomplished? For example, in my primary right now is a hefeweizen with an OG of 1.040. I plan to bottle at 1.010 and prime with sucrose. The ABV before priming should be around 3.9-4.0%. How can I determine the additional alcohol produced from the sucrose? Or is it a negligible amount?

02-07-2013, 02:26 AM   #2
b-boy
16%er

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Jun 2011
The Frozen Tundra, NY
Posts: 4,393
Liked 1220 Times on 797 Posts

Pull a sample and let it sit until the CO2 is gone. Then you can get an accurate FG reading.
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02-07-2013, 02:28 AM   #3
Dirty25

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Jul 2012
Mackenbach, Germany
Posts: 262
Liked 19 Times on 17 Posts

I just added 5oz of corn sugar to one of my recipes in Ibrewmaster and it bumped the alcohol up .2 points

02-07-2013, 02:36 AM   #4
Psych

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Mar 2011
Kelowna, BC
Posts: 780
Liked 37 Times on 34 Posts

Take a sample pre-adding priming sugar, then take one POST adding primary sugar, and calculate the difference. Assuming all priming sugar is eaten by the yeast, giving you carb, you should have your difference.

02-07-2013, 03:05 AM   #5
gstrawn
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Jun 2011
Athens, Ga
Posts: 374
Liked 23 Times on 17 Posts

It is basically negligible. I can't even remember its 4 oz for priming? Equals 112 grams / 342 g/ mol of sucrose= about 0.3 mols x 46 g/ mol= ~15 grams/ ~19 liters= less than 0.01% by weight and even less for alcohol by volume as the density of ethanol is less than that of water. Not precise math but you can see its negligible.

Hope that helps!