A 10% stock Solution of SO2 seems a simple and more accurate way to add SO2 to wine. I make mostly red wine and the SO2 indicator test does not work too well with red wines. With a 10% SO2 solution 6.7 ml added to 19.2 carboy should give me 20ppm. However, I don't feel comfortable adding even small quantities of water to wine. Is there any reason I can't use a stock solution made with a light unoaked white wine instead of water?
thanks Joe
FWIW, my stock solution is 220 grams of potassium metabisulfite diluted to a liter. Freshly bought meta usually assays at ~50% available SO2, so that concentration means I add 20 ml to a 60 gallon barrel to increase the SO2 by
10 ppm.
Worrying about such insignificant details amounts to picking the fly sh** out of the pepper. ;^) Besides, the amount of water added with the sulfite is insignificant when compared to the water required to make up fining agents - and even _that_ isn't significant.
Tom S
Hi Tom Point taken. It looks to me that your stock solution is around 10% SO2. Which I guess makes it a 20% solution of metabisulphite solution. Is there an advantage with this versus a standard 10% (5.7% SO2) solution recommended by some wine books? Thanks Joe
Less water added to the wine. I don't wish to contribute to dilution any more than necessary either. :^)
BTW, that stuff needs to be kept airtight so as to retain its potency. Sulfites are very reactive with air, forming sulfates in the process - which is exactly what it does in your wine to prevent oxidation and availability of oxygen to spoilage organisms.
Tom S
As always you are intriguing. Let me get this straight; you have some data (your own tests, or some other clinical trials?) that suggests that the granulated meta we all buy is actually somewhat less than 50% strength; therefore, you create a solution that is 22% - resulting in an 10% effective solution? Do you test that resultant fluid for free SO2 to verify?
Further to the same point - do you test for free SO2 in your wine? Titrettes (Ripper) or aeration oxidation?
I don't measure my stock solution. I know that I'll be pretty close making it up by my usual method because Ripper on the wine after addition has always jibed closely with my predicted SO2 increase based on a volumetric addition of stock solution. BTW, I got the assay info on meta from The Wine Lab.
Yes, I do measure the free SO2 in the wine (Ripper). That's what really counts, after all. My pH numbers tend to be in the range of 3.4 to 3.6, so if I'm off by 10% or so on the free SO2 it's not that big a deal, since that's close to the resolution limit of Ripper anyway.
Tom S
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