"Paul E. Lehmann" > wrote in message >...
> pp wrote:
>
> > "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
>
> Would be interesting to see some data from Brix values closer to 22 Brix.
> Do you have or could you get data in this area. 25+ Brix values are not
> representative of grapes grown in the East. I am wondering if the error
> might not be non linear and may in fact be opposite for lower Brix juice.

It definitely would be informative, but can't help you there, these
were all the data I could find among my notes. However, the theory is
that in colder climates the alcohol yield is better than in hotter
climates, so if anything, the error should be even more pronounced for
lower B values, more common in colder climates. But that's just a
guess, no data to support that.

Pp