WineXpert Island Mist Alcohol Calc.

[WineNewbie]

When using the SG formula to calculate alcohol content, I've been using the Beginning SG - Ending SG / 7.36 (SG's without the decimals).


Example 1085 - 990 / 7.36 = 12.9%


My question is with the Island Mist Kits, (or any "Back-Sweetened" wine)when you add the F-Pack it brings the SG back up. Do you use the SG reading from before adding the F-Pack, or after adding it to calculate the final alcohol content?


I'm making the Exotic Fruits White Zin. and just finished stabalizing. Wanted to know how to correctly calculate the alcohol.

 

[masta]

John you want to use the ending SG reading before adding the F-Pack or back sweetening for %ABV calculations.

 

[Wade E]

But that will not be accurate anymore if your back sweeting and I dont
know how to figure that out. You are obviosly diluting when sweeting.
Now to make things more complicated. If you add more sugar during
fermentation as you would do to make a port you have to account for
that also as youll be adding more alc %

 

[Steve]

The F-Pack is rather small and there will be very minimal dilution, you may lose 0.1% ABV if even that.


As for adding sugar during fermentation, there are calculations for that.

 

[beggarsu]

Beggarsu ABV F-PAck Calculation

But that will not be accurate anymore if your back sweeting and I dont
know how to figure that out. You are obviosly diluting when sweeting.
Now to make things more complicated. If you add more sugar during
fermentation as you would do to make a port you have to account for
that also as youll be adding more alc %

Final ABV = ABV (1) times Vol (1) divide by Vol (2).

Where:
ABV (1) = ABV determined by SG after fermentation over. (beginning and ending)
Vol (1) = volume of wine before backsweeten
Vol (2) = volume of wine after backsweeten


EG for a wine 11 percent - volume 6 gallons add .5 litres sweetener

11 percent times 22.7 litres divide by (22.7 +.5 sweetener) = 10.76 final ABV


----
This is mathematically correct - doesn't matter what kind of sweetener - ABV is determined by volume (Alcohol by Volume)

SG no longer works after backsweeten to determine ABV because is not arrived by fermentation.