I have two beers (recipes here and here). One is a session IPA, the other is a saison of sorts. They are two different beers fermented with different yeast, but both of them stalled.
The session IPA fermented in primary for a week using Safale US-05 ale yeast; OG = 1.046, FG = 1.026. The saison fermented in primary for 2 weeks using Wyeast 3711 French Saison; OG = 1.091, FG = 1.034.
The IPA should have finished around 1.010, the saison should have been around 1.015 - 1.020. Both fermented out much higher than expected. Here are my ideas on why:
- It got too cold overnight (45-60F) where I ferment, causing the yeast to settle out early (and I didn't rouse them and warm them up because I thought they had just finished normally) - this seems to be confirmed in John Palmer's book How to Brew (p. 446)
- Chlorine in the water causing the yeast to stall (I thought this just produced off flavors, but I don't know)
I don't have any other ideas. I'm leaning toward temperature control being the issue. I woke up this morning to find my 3.5 gal of stout at 58F and fermentation seemed to have pretty much stopped. I turned on the heat and roused the yeast by swirling and it's going again, back up to 68F and bubbling every 15 seconds or so.
Did my ferments stall because of the cold or could it have been something else?
PS - I should add that I made the first version of the tamarind saison last summer and FG was right on track at 1.010; that beer was fermented in August where I had AC set to 68F, and it took a week to ferment.