PP

I have been over the material in this book a number of times with
several people (I thought you were one of them). But - let me try to
plod through it again. Comments interspersed:

"pp" > wrote in message
om...
> "frederick ploegman" > wrote in message
> >...
>>
>> The only thing I find are "pre-pitch" (original gravity) tables. These
>> cannot be used in the manner stated above because it fails to consider
>> the effect that alcohol has on the "post ferment" reading. So far, I
>> have
>> not seen a single answer in this thread that considers this, so the
>> answers
>> thus obtained are wrong.
>>
>> I am hoping that Jack or someone else here has a "post ferment/end
>> alcohol" table that they could share with us. Tables, after all, are
>> nothing more than a simple listing of all of the answers that a formula
>> can provide. They have the advantage that folks that can't even
>> _spell_the word algebra can look up the answers they need without
>> having to understand the math. So - if someone has a suitable formula,
>> it should be no problem converting it to a table.
>>
>> Frederick
>
> Frederick:
>
> I certainly agree with you that alcohol will affect the final sg
> reading, but I disagree with your conclusions in this thread. As you
> say, a table just reflects an underlying formula. There are formulas
> out there that use final sg reading to calculate the PA, so tables
> based on these formulas then reflect both the starting and final sg.
>

Such formulas use an ADJUSTED final gravity and_not_the ACTUAL
final gravity !!

> To take one example, Duncan and Acton's Progressive Winemaking
> mentions a simple formula PA = (Gs - Gf)/7.4, where G is the gravity,
> defined as SG*1000. The constant 7.4 is actually an approximation -

Read this again_veeeery_carefully. G is defined as having a reference of
1.000. This means BOTH Gs AND Gf !! So long as they both share the
same reference point, then yes, this formula will work. BUT (big but),
folks don't understand this and they _try_ to use their ACTUAL end SG
reading when using this formula. If Gf is NOT restored to a reference
point of 1.000 by compensating for the effect of alcohol on the final
gravity reading, this formula does NOT work !! Gee whiz. This is what
I have been_trying_ to explain all along !! From the rest of what you
say here, I suspect that you are still making this same mistake yourself.

> they also give a more complicated formula, where the constant depends
> on the starting gravity, but for simplicity, we can stick with the one
> value 7.4 here.

Not what I use, but "good enough", IF Gf is adjusted.

>
> The point is that this does not falsely increase the amount of sugar
> in the must.

It _does_have this effect when Gf is _not_ adjusted.

>Instead, the formula describes PA in terms of the total
> drop in gravity during fermentation (which directly depends on the
> sugar content of the must).

I would view this statement as wrong in this particular context. Only
_part_ of the total drop is caused by the consumption of fermentable
sugars. The _rest_of the drop is due to the effect of alcohol on our
end SG reading. However, (to avoid another nit) if this statement is
taken to mean that the amount of drop is dependent on the amount of
fermentable sugars available to the yeast, then yes I can buy that.

>As such, it's not better or worse by
> itself than formulas that describe the PA only in terms of the initial
> sg (sugar content).

Wrong. PA is based _solely_ on the amount of fermentable sugars
available to the yeast. Let me say once more - there is NO FIXED
RELATIONSHIP BETWEEN SG AND PA !! SG is a measure of
_total_solutes (not just the sugar).

>Which formula is better is an empirical question -

Nope.

> any formula gives only a rough estimate of the final alcohol,

Estimate yes, rough no.

>so the
> quality of any formula would have to be measured against decent amount
> of real data.

Every country and every state that has any interest at all in having a
winemaking industry has government funded labs which lack for
nothing by way of facilities and the best and most modern equipment.
These are staffed by people who spend entire_life_ times dedicated to
winemaking research. This being the case, how can you even_imagine_
such data does not already exist and has not already been incorporated
into the things we use ?? (eg the PA scale on our hydrometers, etc..)

>
> To continue with the above formula - since it's linear in terms of the
> total gravity drop, we can use the method that Jack described and
> shift the final gravity to 1000 (sg to 1.000) if we shift the initial
> gravity by the same amount.

Wrong, wrong, wrong !! The final gravity_does_ need to be shifted,
but the original gravity is_not_effected by the presence of alcohol so it
does_not_have to be shifted. (It_already_has a reference point of
1.000) Which of course is my whole point here.
BOTH readings have to share the SAME reference point !!

>And then a table that is based on this
> formula will show the PA reading for the adjusted Gs - the adjustment
> is needed because it allows us to start tabulating from sg 1.000.

Nope - see above. In view of my previous answers here, I won't go
on with this at this time. HTH and HTMS

Frederick

>
> Pp