pp,

Thanks for the discussion. I don't disagree with any of the points you
make. I especially agree that there's no reason not to include final sg's
that are under 1.0 in the alcohol content calculation. It seems to me that
only by considering the total sg drop can you really estimate the overall
compositional change during fermentation. But I know others out there
disagree.

Steve


"pp" > wrote in message
ups.com...
Steve:

No fight here. I noticed the 2 results closely correlate but that
could just mean one formula could be derived from the other the real
test is judging the computed results against measured values. The
practical problem with this is we don't seem to have ready access to
measured alcohol values so it's hard to support any result well.

Some people discard D&A's work because they argue considering the
final gravity is plain wrong because anything that goes under sg 1.0
is just the effect of alcohol created from the sugar (which is
captured by initial s.g. value). That would also apply to Balling's
formula. This is more pronounced for wines where often the final s.g.
can get to 0.990 for dry wines.

Personally, I think that argument is faulty because it ignores how the
formula was designed - it's just as easy to base the PA values solely
on the initial s.g. as it is to base them on the difference between
final and initial s.g. The latter does not artifically "add sugar
that's not there", it just incorporates the fact that the sugar
progressively changes into alcohol and bases the calculation on that.
The results will not completely agree but it's just an estimate anyway
because the actual alcohol depends on many factors that cannot really
be measured in practice.

That said, based on the s.g. values of the grapes and juice we
routinely get from California these days, I think the D&A formula
exagerates the PA values by about 0.5-1% of abv. Again, this is
imprecise as it's based on taste comparisons of my wines with
commercial wines with stated alcohol value, but it works for me and
that's really what matters in the end .

You might want to check out this page: http://www.brsquared.org/wine/
in the Calcs/Info section, it has some other formulas from the
literature. Actaully, given that you're already showing 2 different
values anyway, it might be of real value to collect all the different
formulas you can get hands on and add those to the applet, kind of
like what Ben has in his table but more extensive. That would give
people a full range of PA results comparison in one place; I think
that'd be really useful.

One final note on the subject of precision - I think all calculations
should be round up to give the PA values in 0.5% increments. Anything
more than that gives a false impression that the computed value is the
exact amount of alcohol in the wine, which is at odds of what the
formulas can really do.

Sorry, I've made this longer than I wanted - I keep promising myself I
won't get involved in these debates anymore but it doesn't seem to
work...

Pp


On Feb 19, 6:17 pm, "Steve Gross" <gross**at**pdq**dot**net> wrote:
> Okay, I didn't mean to start a fight! But in answer to Pp's comment about
> the Balling formula, yes, there don't seem to be any references to its use
> in the context of wine, at least on the web. But when I tested it, the
> results were remakably similar to the Duncan & Acton formula. And when
> you
> compare equations (5) and (8) on my documentation page
> (http://web2.airmail.net/sgross/fermc...c_alcohol.html) you'll see
> that both formulas have a very similar form. I found these comparisons
> somewhat compelling, so I included both formulas in the calculator.
>
> Steve
>