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Chaptalization during fermentation calculation

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David Violante

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I'm looking for a way to come up with the final potential ABV of my wine. The caveat is that I added sugar during fermentation as I realized that the original SG was fairly low. Yep. I should have just added up front.

I did take readings along the way so I know what initial, pre- and post-additions were.

If:
Initial Reading - Final Reading * 131.25 = ABV%
(1.080-0.998) * 131.25 = 10.76%

Then:
((initial reading - preaddition reading) + (postaddition reading - final reading)) * 131.25 = modified ABV%
((1.080 - 1.050) + (1.070 - 0.998)) * 131.25 = 13.39%

Does that sound about right?
 

sour_grapes

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It will be close. However, you did not account for the change in the volume due to adding sugar. Best would be to figure out how many oz. (or mL) of ethanol there was before you added sugar (for which you will need the initial volume), then figure out the new volume, then figure out how many additional oz. of ethanol resulted from the second bout of fermentation.

But it will be close; I would wager the effect I am speaking of is about a 4% effect (that is, say, 14% --> 13.4%). Just a guess.
 
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David Violante

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Hmmmm... I didn’t accurately measure the volume past “it’s at the 1 gallon mark on the fermenter”. When I mixed in the sugar I used some must to dissolve the sugar so I didn’t add water to the must. I’ll have to figure out those calculations. I did this with a 1 gallon BlackBerry, and two 3-gallon (What’s left after having pressed) DeChaunacs.
 

David Violante

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Thank you all ~ in the end, you are right, it won't matter much for practicality's sake.

I'm asking more for the understanding of the math and science of it all. I very much appreciate all the nuances of the art and the amazing perspective of how and why each person does what they do. If I can understand the "why" it helps me on my own journey. Super huge thank you to everyone willing to help me figure it out - including the prodding when "it doesn't matter..." and I may be too far into the weeds.
 

Ajmassa

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Well if looking to dive into the numbers just for fun then FermCalc will give you alot of the specs. Just plug in your known amounts and will tell you what the new volume would have been.

theoretically would have used .4928 lbs of sugar bringing 1gal up to 1.0366 gal. There’s also multiple accepted abv equations which vary slightly. No clue which one is the most commonly used F2B5028D-A516-41B7-A7B3-2B75A06BF2B3.jpeg1EAD94DD-213E-4940-840A-669B548696BA.jpeg
 

David Violante

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I’ve saved it to my favorites...! Thank you all again~ I really do appreciate understanding what’s going on and why.
 

winemaker81

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This is funny -- a friend asked me a question like this last night, and I spent 20 minutes hunting down calculator sites. I found what appears to be 4 distinctly different formulas which all differ a bit. Then I read this thread and FermCalc shows 4 methods ...

From what I've read, the calculation of ABV is not a linear solution and it varies by the amount of alcohol present, e.g., a calculator for beer will not produce an accurate results for wine.

If commercial wineries are given a 1.5% ABV variance in each direction, then for a 12% ABV wine, that's 12.5% (of the base ABV) in either direction, a total span of 25%.

In the FermCalc example, the average is 13.8% ABV. The variance from the average is 1.5%, meaning the overall span is 3%. That is far more accurate than is legally allowed.

Any of the 4 methods is basically spot on, or as @Johnd suggested, use the average.
 

salcoco

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the variance is + or - 1.5%abv a span of 3% or 10.5-13.5 if 12 is the mean not 1.5 times 12
 

Rice_Guy

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a variation of plus 1.5% and minus1.5% is actually a 3% variance.
 

winemaker81

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the variance is + or - 1.5%abv a span of 3% or 10.5-13.5 if 12 is the mean not 1.5 times 12
Gotcha -- I (obviously) misunderstood your first post.

I stand corrected -- FermCalc is 100% spot on for the acceptable commercial variance.

I assume this is USA law. Is it federal or a specific state? Thanks!
 
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