One of my 2003 batches (mixture of CA central valley Cab Sauv and Alicante) has been bubbling away pretty steadily in the carboy with what I thought was MLF (it's close to 3 weeks since it went dry). I had been too busy to check it much the last 10 days, and when I finally took a wiff there was a lot of H2S coming off. Since I had some 1% CuSO4 solution handy from a couple of years ago when I had my first H2S problem, I hit the wine with what should have been about
0.07ppm and racked off the lees. The lees themselves did not smell very strongly of H2S.Since that racking, there has been no detectable bubbling. I'm curious as to whether the bubbling I saw could have been H2S being produced rather than MLF. Or was it likely MLF, and the racking and/or CuSO4 addition stunted or killed the MLF process? Or is 3 or 4 days just too little time to be seeing bubbles being given off again (the tiny ones in the wine, not the airlock bubbling) even if MLF is still active?
Thanks, Richard