Ray's assertion is correct. While simple conversions tend to work very well
over time for established operations,
Potential Alcohol calculation is by no means straightforward in the larger
sense. The conversion factor of 0.55 to calculate
Potential Alcohol from Brix is a pretty standard industry value and has
worked well for me in general. Strictly speaking, every
gram of sugar consumed by the yeast will liberate at most 0.511 grams of
ethanol. This means that the 22.8 Brix could yeild a potential 11.65 w/w%
Ethanol which is about 14.3 v/v%. To achieve this level of ethanol after
fermentation would
require absolutely complete extraction of all sugar, 100% yeast efficiency,
0% evaporative loss, and
yeast fermentation to 0.00% residual sugar. Needless to say, this is highly
unlikely so usefull "conversion factors"
like the 0.55 discussed have become commonplace. I believe a range of
conversion factors of 0.54 - 0.62
would cover the vast majority of observed results in the industry globally
resulting in a v/v% ethanol range of
12.3% to 14.1% depending on the vast array of variables that can affect
conversion, efficiency, and loss.

CHEERS TO ALL!!

Aaron

"Ray" > wrote in message
news
> I have to differ with you on the interpretation of potential alcohol. The
> majority of tables of PA / SG give the PA assuming the SG drops to 1.000.
> This is not dry. That is why negative numbers are given on hydrometers
for
> PA when the hydrometer goes below 1.000. If you just go by the beginning
SG
> you can have a 1-2.5 points error in your PA. The only table that I am
> aware of that assumes fermentation to true dryness is that of Duncan and
> Acton though I have been told that UC Davis also takes this into account.
>
> Ray
>
> "JEP" > wrote in message
> om...
> > (Galileo) wrote in message
> . com>...
> > >
> > > I thought I understood Brix, but maybe not. The starting SG is 1.097
> > > which is a PA of about 12.7% alcohol. And, so far, my final SG has
> > > usually been below 1.00, usually about 0.990. Wouldn't this be a
> > > final alcohol level of about 13.7% ?
> > >
> > > Thanks,
> > > Galileo
> >
> > The hydrometer's PA reading prior to fermentation gives you an
> > estimate of the alcohol if all of the sugars are consumed. So you will
> > get approximately 12.7% alcohol when the final SG of the wine is down
> > in the .992 - .995 range. If the fermentation stops and your final SG
> > is higher, not all of the sugars were consumed (or there was a
> > significant amount of other disolved solids in the must) and the
> > alcohol content will be less than the original PA.
> >
> > Andy
>
>