H2S (Rotten Egg) Smell during mid primary

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Mar 5, 2024
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Hello -

I have a viognier juice going on right now using QA23 yeast and currently at 1.60 (from 1.100). The fermentation started strong and as such I reduced my controlled temperature to 55f, after about a week it smelled fine. Until yesterday I started to smell some eggs. Nutrient isnt the issue here I believe because the night right before I started smelling the faintest hint of H2S I added my last (half) remainder of Fermaid O at 1.700. I know the QA23 recommends 58f+, but can be fermented down to 50f under the right circumstances. I think the yeast struggled to ferment at this temp so I slowly brought it up to 60-61f overnight and swirled the carboy a good bit to introduce some O2, but today I can certainly smell the H2S and clearly is not just a "hint" anymore.

2 Questions:
#1 - Is there anything else I should do, or wait another day to see if it clears and ferments a bit more stable before performing any other corrective actions.

#2 - I wanted to sur-lie my viognier, at this point is it not recommended to do this as I have encountered H2S?
H2S can be present before you smell it. It's entirely possible that adding nutrient prevented the yeast from making more, but you need to deal with what you have.

Stir the wine well, running a fan. If it stinks, you know you go it. Add K-meta, and stir again. If you caught it early enough, and it appears you did, that may solve the problem.

You'll want to rack off the gross lees 3 to 5 days after you're sure fermentation is complete. You can age sur lie on what drops after that.

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