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New Gravity after adding Sweetners

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JMSetzler

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What's the procedure for calculating alcohol content after adding additional sweetners? I fermented a batch of Apfelwein, and in order to make it into something my mom would drink, I had to add a bunch of frozen apple juice concentrate. I added about 6 large cans of concentrate and then one additional cup of corn sugar to my 3-gallon batch of Apfelwein.

My original gravity before fermentation was 1.062.
My gravity after fermentation was 0.996.

At this point, I added potassium sorbate to stop any additional fermentation.

I added 6 cans of apple juice concentrate plus 1 cup of corn sugar.

My new gravity at this point is 1.032.

If I figure the alcohol by volume based on the difference between 1.062 and 1.032, it comes up to 3.9%, which may be accurate, but it doesn't seem like it would be accurate since I only added less than 1/2 gallon of content to the 3-gallon batch...
 

Yooper

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No, you figure the ABV by OG-FG and then multipling it by .131 or so. (1.062-.996) x .131 = approx 8.6% ABV

Sweetening (or not sweetening) doesn't change the ABV, since it doesn't ferment out and increase the alcohol content.

Since you added 1/2 gallon (diluted it), though, that's not entirely accurate. You could figure out the dilution, if you knew the exact amount you added.
 

Tusch

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You didn't affect how much ethanol you created by backsweetening. So you would calculate your abv by (1.062-.996)*131 = 8.646%

If you want to be precise though, that would be for your initial volume prior to backsweetening. So your new abv would be .08646(X initial Volume) = Y new %(Initial Volume + backsweetening volume) plug in your volumes and calculate your Y new abv %
 

MacBruver

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If you're considering 1.032 your FG, your OG is actually 1.062 + (1.032 - 0.996) = 1.098. Of course that is just a lot of work for nothing, since you end up at the same place... 8.646% ABV. To calculate the change in ABV by adding water:

(original volume * alcohol percentage) / new volume

if you added half a gallon:
3 * 0.0846 / 3.5 = 7.41% ABV
 
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