"pp" > wrote in message
om...
> "frederick ploegman" > wrote in message
>...
> >
> > I wish you luck, Pp. I, for one, will be very much surprised if the PA
> > scale on all of the world's hydrometers turns out to be invalid.
> >
> > Frederick
>
> Alright, here is how the hydrometer PA scale does against some real
> data. The numbers are from info sheets provided by Napa, Sonoma, and 1
> Washington state winery. The wines are marked R (red) and W (white) as
> this is significant.
>
> The columns a Brix, final alcohol, PA per hydrometer, delta
> (hydrometer - actual).
>
> The PA per hydrometer was calculated by B * (12/22) = B * 0.545 (as
> 22B = 12PA).
>
> The table is ordered by the delta.
>
> Where B is given as a range, avg value was taken for simplicity.
>
> Type B Final PA Delta
> R 25.5 13.5 13.9 +0.4
> R 26-27 14.5 14.5 0
> W 25.6 14.2 14 -0.2
> W 25.2 14 13.8 -0.2
> R 24.8 13.9 13.6 -0.3
> R 24-25 13.7 13.4 -0.3
> R 26.8 15 14.6 -0.4
> R 24.2 13.6 13.2 -0.4
> R 26.4 15 14.4 -0.6
> W 25 14.5 13.7 -0.8
> W 23.8 13.9 13 -0.9
> W 23.5 13.9 12.8 -1.1
> W 23.5-25 14.5 13.3 -1.2
> W 23.5 14.2 12.8 -1.4
>
> Average delta all: -0.53; reds: -0.23; whites: -0.83
>
> I'd say not too good overall, particularly for whites. The higher
> alcohol in whites vs. reds makes sense and is well supported in
> literature. But the formula systematically underestimates even reds in
> this sample. Out of 14 wines, 6 are outside of the reasonable +-0.5
> delta, with the worst case being -1.4 (that's Napa, Matanzas Creek
> Sauv B 2001).
>
> Based on this, I think I could argue that the PA scale on all of the
> world's hydrometers leaves something to be desired.
>
> Pp

Hi Pp

No serious student of winemaking would consider this to be "real data".
But I know that you are serious about this and I will try to give you
a serious answer here. To this end, let me give you an easy way to
evaluate this data for yourself.

Keep in mind that the maximum *theoretical* conversion rate is
about 0.60, and the maximum *realistic* conversion rate is about 0.55.
It is this realistic rate that we find on our hydrometers.

All you have to do is divide the end alcohol by the original BRIX to
see how this data compares to reality.

In your fist example we would divide 13.5(ABV) by 25.5(BRIX) and
get 0.529. This is slightly less than the expected 0.55 rate and would
lead us to expect that a small amount of sugar was unconsumed and
was left in the wine as "residual" sugar.

In your last example we would divide 14.2(ABV) by 23.5(BRIX) and
get 0.6043. This exceeds even the theoretical maximum (even
without _any_ losses) !! Obviously there is something seriously wrong
with these numbers.

I might also point out that in at least 3 of these examples they are unsure
of their original BRIX numbers, which automatically indicates that this
"real data" isn't credible.

There is of course a much easier way to do this. Since the "realistic"
calculations have already been done for us and appear in the PA
scale on our hydrometers, simply compare the end alcohol to the
original PA for that wine. If the end alcohol exceeds the predicted
(potential) alcohol, you automatically know that something has gone
wrong with your end alcohol calculation.
HTMS, HTH

Frederick