"Tom S" > wrote in message >. ..
> "LG1111" > wrote in message
> ...
> > I'm still confounded why I
> > get such screwy discrepancies when I test a freshly crushed must versus
> when I
> > wait for 4-5 days of fermentation. I virtually always see lower pH's
> after 4-5
> > days, and the TA's are often higher. I'm getting to the point where I
> think my
> > acid corrections are hurting more than helping.
>
> If you failed to degas your sample taken during fermentation it may very
> well read higher TA than initially. I'm not sure about the pH going down
> for that reason though. Try bringing your samples just to the boiling point
> to drive off the dissolved CO2 before you run your measurements and see if
> that helps.
>
> BTW, when doing an acid addition always try it on a small sample first and
> _taste_ it as a sanity check.
>
> Tom S

Lee, as Tom says, at 4-5 days of fermentation your wine is going to be
high in dissolved CO2 which means carbonic acid in your wine which
will both raise TA and lower pH. So that's a very difficult time to
make reliable measurements of either. As Tom also says, if you want
to try to measure either TA or acid during or just after fermentation,
you need to take measures to degas your sample, by boiling and/or
shaking vigorously. Your apparently increased acidity may well have
something to do with dissolved CO2. All of the advice you've gotten
on taking care with additions is good, though - whether it's sugar,
SO2, acid, or anything else, putting it in is a lot easier than
getting it out ;^)

- Mark W.