DD, as you say they are all close. Do you know that the ABV as stated on a bottle of commercial wine can be plus or minus 1%? So what you see on those bottles is not dead on accurate either.

But, if you really want to do an accurate job and don't mind sacrificing some of your wine, try the following:

1. Take an accurate sample amount, say one pint.

2. Put the sample in a pot on the range and turn on the heat to medium.

3. Bring the wine to about 180 degrees F and keep it there for at least 15 minutes.

4. Remove from the heat and measure the volume of the remaining liquid.

4. Alcohol boils off at about 175 degrees F, water at 212 degrees F, so the change in volume will be the alcohol that is vaporized.

6. Divide the amount lost by the starting volume to give you the % alcohol in the original wine.

PS: This is a good method for determining alcohol when you forget or did not take an initial SG reading.

I don't think this will give correct answer. When 1 ltr alcohol is mixed with 1 ltr water, the resulting volume of the solution is not 2 ltrs. It is less than 2 ltrs.

I don't know the exact % by which the volume of solution is less than 2 ltrs. But I am sure it is less.

Suppose it is 1.8 ltrs (hypothetically); and you boil it at 185 degrees for 15 minutes, and then measure the volume of remaining solution after evaporation of alcohol. It will come out to be 1 ltr.

By your method, the volume of alcohol will turn out to be 0.8 ltr... when actually it was 1 ltr.

I think, the correct method will be to find out the weight of solution before and after evaporating alcohol. Subtracting the final weight of solution from initial, you will get weight of alcohol. And then convert that weight into alcohol volume. That will be the correct volume.

Then you can find its volume % to solution volume before evaporation.. and you get your ABV.

I must declare that I haven't done this. I am no scientist, or a mathematician. I am just applying the logic on available facts.

Another correct method seems to be to distill and collect the evaporated alcohol and actually measure its volume.