"Gerald Todd" > wrote in message
news:1108751775.78920acfb063b537ea4751dda3f090f1@t eranews...
> At what points should you test for SO2?

Right after fermentation and just before bottling. If you're barrel aging,
you need to check it every few months too.

Also, I've read about the
> relationship between pH and SO2, which leads to my next question- If you
> test and determine that both SO2 and TA need adjusting, is there any
> standard way of adjusting them?

TA first; then check the pH and adjust the free SO2 according to that.

The way I understand it, free SO2 will go
> up as pH goes down.

Not true. Free SO2 is independent of pH within the normal range for wines.
You're thinking of _molecular_ free SO2, which IS pH dependent.

The three forms are (1) total SO2; (2) free SO2; (3) molecular free SO2.

Total SO2 is just what it sounds like: all SO2 in the wine. Much of that
total is bound to other things in the wine in such a way that it is not
available to protect the wine.

Free SO2 is available to dissociate into molecular free SO2, but that is a
pH dependent phenomenon. The lower the pH, the more this dissociation
occurs. The amount of molecular free SO2 needed to protect a wine from
spoilage and oxidation is roughly 0.8 ppm. At pH 3.2 it takes about 20 ppm
free SO2 to produce 0.8 ppm molecular SO2. At pH 3.6 it takes about 60 ppm
free SO2 to produce that same 0.8 ppm molecular SO2.

Tom S