Serious about Hydrogen Sulfide

Well, the new strain of yeast that I just tried in a batch of Traditional Wildflower mead (R-HST) lives up to the Lallemand description of behavior. It requires a medium amount of nitrogen (most of the yeasts we use are "low" on their scale), and when nitrogen deprived, it produces significant H2S. I can vouch for that personally! :angryfire:

Despite using about 1-1/2 times the amount of DAP and the usual recommended dose of Fermaid, in the final 1/3 of primary fermentation I started sensing a noticeable H2S smell, which has only gotten worse with each passing day (OG was 1.128, the issue started around 1.050, and now I'm down in the vicinity of 1.020 with fermentation still proceeding slowly). Fermentation has been going on for about 10 days at this point, and was at an average temp of 72F, with an average pH of 3.4. This much H2S in a mead batch is definitely outside my experience, and I'm afraid if left untreated I'm likely to have to age this batch for a decade or two before all the sulfide dissipates and the mead becomes drinkable.

So, I've seen archival posts about using solid copper, copper sulfate, or a combo of copper sulfate and ascorbic acid as potential solutions for this problem, but those posts quote vintner sources. My questions for you all are, has anybody actually tried this on a mead yet, and how well did it work?

Oh, and the obvious side note on R-HST as a yeast for mead -- feed it well, or expect some rotten egg scent to come wafting out of your primary bucket towards the end of fermentation!

Generally I only stir during the first third of fermentation, so as to not introduce too much O2; I don't want oxidized, "sherry-fied" mead. Still, just to see if I could avoid more extreme measures I did slowly stir to de-gas this evening (SG is now down to 1.017 and the fermentation is proceeding very slowly -- I'm pretty much up at the listed alcohol tolerance for R-HST). I got a lot of foaming (as expected), a big whiff of H2S, and then things settled down. At present, which is about an hour after the stir, I don't smell any appreciable H2S in the brew room (which is a basement closet -- small enough to allow any aromas to accumulate until they're noticeable). I take this as a good sign! 8)

Maybe more drastic countermeasures won't be called for after all. Still, I have to admit that I'm uncomfortable about stirring any fermenting beverage this late in the primary. I won't do it again, unless you think otherwise, that is!