On Nov 26, 2:46 pm, "Paul E. Lehmann" > wrote:
> Joe Sallustio wrote:
>
> >> Hi. Is there a special starter I should use to
> >> re-start this? Room temperature shouldn't be
> >> an issue - it's being kept in my pantry so it
> >> is always warm enough.
>
> > Steve's post already gave you great advice and
> > the correct value of
> > 'potential alcohol' for 1.100SG. (My tables
> > came from NBS so I know
> > they are right.) The only thing I would expand
> > on is the amount of
> > time to give it to get going. Starters need to
> > get going really well
> > before you add them to the total volume. I
> > keep doubling the volume of the starter and let
> > it get back to fermenting strongly.
>
> >>13% ABV for an apple wine might be a little
> >>heavy duty; if this died at around 9 or 10 % I
> >>might be happy with that. I show that as 1.022
> >>to 1.029 S.G.
>
> > bobdrob,
> > I show 1.115 as 19.3 % ABV; I have the book at
> > home that probably
> > takes them higher; I have spreadsheet I made on
> > my work PC. I can email you the spreadsheet.
>
> > Joe
>
> Joe, are you sure of that? I quick check on my
> program shows 1.115 SG to be equivalent to 15.78
> Brix and the PA to be 15.78

Hi Paul,
Yes, I'm sure to a rounding error. I have the book now. Baume
(modulus 145) is what most people refer to as 'potential alcohol'. I
show 34.3 brix =1.14985 S.G. =18.90 Baume 145 at 20C.

I really think the confusion comes from two places.

One, alcohol concentrations can be measured by volume (V/V or ABV) or
weight ABW) . Most refer to ABV now and don't mention ABW. ABW is
about 20% lower than ABV so maybe that is what your chart is
calibrated to, weight, not volume.

More important, the potential alcohol scale is _exactly_ what it says
it is. It is only a crude measuurement of potential alcohol. There
in no way to measure density changes and categorically align them to
actual alcohol content with precision. The type and quantity of yeast
used, the temperature of fermentation and the storage conditions all
play into final alcohol content. PA does not consider dry extract
content either, most of which is acid and is variable to an easily
measurable degree. It can't. Wine can have a little acetic acid and
can have a whole lot, that affects the density too.

All that said, if you make the same wines the same way with the same
materials you can probably predict pretty well what your final alcohol
will be. I use those values as a rough guess of where things stand
and that is it. As I see it, this scale is useful to monitor
fermentation progress and very little else because then is a
marginally relative measurement. Even then the acids are changing to
a measurable degree and all my hydrometers measure is total density at
a given temperature.

As to why it doesn't go below zero, I'm pretty sure Baume calibrated
his scales with salt solutions so by definition they can't go below
zero. The final gravity is much affected by dry extract content so
where a dry wine will end up isn't just a matter of alcohol, it's the
acid content and other dissolved solids too. The best relatively
cheap way to measure alcohol is by distillation and hydrometry; that
way you are measuring relatively pure components. The best cheap way
to measure residual sugar is Clinitest tablets.

Physics is cool but I treat the PA scale like Myth Busters; I watch it
but I don't lend a lot of weight to it...

Joe