pH vs. free SO2 in concord wine

[reefman]

Can we discuss pH vs. Free SO2 levels....this is the first time I've heard this mentioned. What's the relationship between the two, and how do you calculate ppm of SO2 required, based on pH?

 

[cmason1957]

I am going to post two links and then summarize what I think they say.

http://morewinemaking.com/public/pdf/so2.pdf

http://www.accuvin.com/pHSO2Links.pdf

PH FREE SO2 required
2.9 7 - 11 PPM
3.2 13 - 21 PPM
3.4 20 - 32 PPM
3.6 31 - 49 PPM
3.8 49 - 79 PPM
4.0 78 - 123 PPM

There is also a formula in there to help you decide how much to add:
grams of metabisulfite to add = ______ppm x 0.00657 x _______gallons of wine, juice or must
Thus, for a 22 ppm addition to 5 gallons of wine, you will add:
22 x 0.00657 x 5 =0.72 g of metabisulfite.

Now what do I do. I keep my PH in the "normal" range of 3.2 to 3.6 then prior to starting ferment with grapes,

juice, fruit, etc. I add 1/4 tsp and at every other racking, which means about every 3 to 4 months after fermentation is complete I add another 1/4 tsp. If you have the equipment to measure what you have, I would use that and determine what I really needed to add.

 

[Stressbaby]

For those making 1 gallon batches, 1 Campden tab raises 1 gallon 66 mg/l (66 ppm).