Taking the SO2 Plunge

New pH meter

Got a pH meter + Flawless

In the interest of being more precise in my knowledge of my own wines, I bought a pH measuring devise a couple months back. I hadn’t used it so far on the Petite Sirah and I was starting to think that I might not at all. After all, what would I do with that information? I knew that the pH level can be indicative of the sensory aspect of a wine, but I don’t want to be messing around with that too much. I also knew that the pH level is a factor in determining the amount of SO2 to add to the wine, but I hadn’t decided where I was going with the SO2 approach just yet.

In parallel, I’ve been reading Flawless, by Jamie Goode. Goode is a writer who’s at the very least, natural-wine-adjacent, or has an open approach to those techniques as potential methods for creating good wine. So, I undertook that book to educate myself on some of the chemical origins of common flaws in wine, to improve my own tasting knowledge and maybe help out my winemaking on the side.

Going through the sections on brett and oxygen management gave me a fright though. Would I risk my entire batch by underdosing or not dosing with SO2? Doing so would certainly be the safe approach. I also considered the fact that I know nothing about the vineyard or growing conditions of the grapes I used and I already used commercial yeast, so to pursue some zero-zero dream by holding back SO2 just wouldn’t work.

So, I decided to take the SO2 plunge.

Doing the measurements

I researched different charts for the addition of SO2 based on pH levels and found a few that generally seemed to agree with each other. Yesterday, I went down to the basement and used the Titrets to measure the current free SO2 in the RP-15 and D21 batches.

Titrets is barely useful with a red wine, I’ve learned. From the best I could tell, it was saying that the wines had 35 and 30 ppm free SO2, respectively, when I hadn’t added any. That does not seem right. But, it’s all I have to go on. I then tested the pH. Both carboys came in at a little above 4 — 4.06 and 4.13! This also seemed quite high! According to the SO2 charts I was using, I needed to be aiming for 78ppm free SO2.

OK, so weirdly high free SO2 and weirdly high pH. I still have no idea what all this means, but I’m just trusting the numbers I’m seeing at this point. I added SO2 to bring these guys up to about 75ppm (my measurement tools are still not very precise) and put the airlocks back on.

Now, I’ll wait a couple months before seeing what’s going on in there.


Tasting

I also got a chance to give them a try. The D21 tannins have softened a bit, which is good to see and the RP-15 remains comparably fruity. I’m thinking I’m leaning toward keeping them separate at this point.

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