Hope this works this time..........
Ooops...Nope. With the alcohol gone, seems I would have to add 3 points to the difference in order to get the best estimates when using the "old" formulas (a la CJJ Berry). (eg. to compensate for the 3 point allowance for acid used in the BRIX calculation). These "old" formulas were based on the assumption that the acid and alcohol would cancel eachother which of course isn't true or we would never get readings below 1.000.
FWIW - For dry ferments, no calculation is required because the original PA already tells us how much alcohol the wine will have when (if) all of the sugar gets converted. So - the only time we need to calculate is for RS wines/musts. With sugar, alcohol, and acid all present when the post pitch reading is taken, it is then a matter of sorting out how much influence each one has on the single SG reading we have to work with.
I no longer have my books and my memory sure ain't what it used to be, so I think I better shut up and let you guys figure this out...........HTH
Frederick
Steve, Pp, et al
>
> Why not try that "boil off the alcohol" procedure that someone
> mentioned here earlier. With the alcohol gone and the "before
> and after" readings restored to direct comparability, any of the
> old formulas that ignored alcohol completely should then work.
>
> Never tried this myself. Just found it easier to compensate for
> the alcohol numerically. HTH
>
> Frederick
>
>
>> 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:
formatting link
>> 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
>>
>>
>> >>> 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
>>>
formatting link
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
>>>
>>
>
>