Hi Bill,

My initial calculations were incorrect.

Part of the problem is that my first TA test was a bit inconclusive. It
was done within 24 hours of intial crush, but by that time, colors were
already clouding up the must, making it difficult to tell when I'd
found the right TA level. Somewhere between .55% and .65%. It was
pretty hard to determine exactly when the test sample turned gray, and
not just a "tint" of gray.

Another aspect is that I have two vats of must. One with about 16
gallons, the other with about 5 or 6 gallons. Last night, the larger
vat had much higher pH, because of more potassium being leached out of
the extra pomace, while the smaller vat had consistenly lower pH (by
..15!) due to less pomace.

My challenge was to calculate the proper amount of Tartartic to add,
understanding the smaller vat would need proportionately less than the
larger, in order to achieve balance between the two. But then, I
considered the fact that throughout ferment, the two vats will develop
their own unique pH anyway, since there is more pomace in the larger
vat, etc. So I ended up figuring that if the smaller vat were to have
lower pH, and the larger a higher pH, it might make for a bit of an
interesting blend once primary was done. And, even if the larger vat
ended up with a much higher pH than the smaller vat, by blending the
two after primary, I'd achieve a bit of balance.

So. I added a total of 30.4 grams Tartaric acid to the smaller vat,
about 6grams per gallon. This resulted in more or less a pH of 3.5,
down from the 3.75. It was difficult to get an accurate read, as the
acid was not evenly distributed throughout the solution, even after
stirring for many minutes. I took 15 different samples, ranging from
3.3 to 3.6, 3.4 to 3.7, and in the end, averaged them all out to about
3.5. Depending on the accuracy of the TA test, this would put TA now at
..8% to .85%, and while by itself, that might a bit high, it should
balance out when blended with the larger vat.

To the larger vat, I added a total of 136 grams of Tartaric acid, about
8.5grams per gallon. This reduced pH from 3.95 (it had gotten pretty
high, even 4.00 in some portions of the vat) down to 3.8, and increased
TA by .21%, to .76% to .81% (again, depending on the actual, initial TA
test).

I then averaged these out.

6gal. @ pH 3.5 + 16gal. @ pH 3.8 = 22 gal. @ pH 3.71

6gal. @ TA .82% (avg. of .8 to .85) + 16 gal. @ TA .78% (avg. of .76 to
..81) = TA .79%

These figures look fine to me. Even after Malo, if pH is boosted by
..25, a final of about 3.9 should be fine, given the wine isn't intended
for more than a few years' ageing.

Fermentation is just 12 hours in, so if I still need to boost Tartaric
a bit more, I could... I'm just questioning the need for it.

Thanks again for all your helpful input.

David

p.s. the juice tastes great. I can taste the acid through the
sweetness, so I think overall it's balanced.



William Frazier wrote:
> David wrote "I went ahead and have added more tartaric acid. From my
> calculations,
> the must should now be around pH 3.66 or so, with about TA .77%-.8%."
>
> David, did you actually take a pH reading? Ideally your starting pH would
> be low enough so pH after malo-lactic fermentation is reasonable.
> Malo-lactic fermentation will raise pH by about 0.25 pH units.
>
> "For this second round, 61 total grams for the 20 gallons (~3g/Gallon,
> or about .8g/L). Total Tartaric added was about 1.6g/L"
>
> If I follow your acid additions correctly you first added 3.0 grams per
> liter tartaric acid to 20 gallons of juice. This works out to 227 grams of
> acid. Then you added 61 additional grams. A total of 288 grams acid added
> to 20 gallons (75.7 liters) of juice or 3.8 grams/liter. Add this to your
> starting 6.0 grams/liter acid and you may have an acid content of 9.8
> grams/liter or 0.98%TA.
>
> How does the juice taste?
>
> Bill Frazier
> Olathe, Kansas USA