I can still smell just a little bit of H2S.
So this is hopefully the last 0.1 ppm of Cu. The total added is 0.3 ppm, way under the legal limit for added Cu, and also under the limit for residual Cu. Actually, probably no more than 0.1 ppm residual is left, since I can still smell the H2S. The rest of the Cu has bound to the H2S and precipitated out.
I can still smell H2S in the wine, but much lower level.
So 0.1 ppm more copper sulphate.
Well, the H2S (rotten egg smell) is still with the wine. I tried a side by side trial using copper sulphate fining.
Using a pipette, I put 1 ml of 1% copper sulphate (way more than allowed) into one sample of wine (see picture). In seconds, the H2S smell was gone. This means that the copper sulphate will clear up the problem. I didn’t drink it…
Copper sulphate fining is common in commercial wines, but is not allowed in organically made wines. I don’t want to add it…but at this point it is either add it or pour the wine! imagine being an organic commercial wine maker with 1000 gallons with this problem…what would you do?
Copper sulphate as an additive is allowed 6 ppm (calculated as copper). The maximum residual copper sulphate is 0.5 ppm (as copper). The copper sulphate binds with the H2S, and precipitates out, leaving less copper than you added.
All the books say that 0.15 ml of 1% CuSO4-5H2O per gallon = 0.1 ppm.
I will do another post later on what is allowed in wine…you would be surprised.