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:

  1. 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)
  2. 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.

  • I'm very new to home brewing, but I just read an article from Northern Brewer on this exact subject. Hopefully it can answer some questions for you: northernbrewer.com/blogs/extract-brewing/…
    – Gogeta70
    May 5, 2019 at 22:24
  • @Gogeta70 Interestingly, the author of that article says to use US-05 or 3711 to finish out fermentation, and those are the two that I used initially. May 5, 2019 at 22:31
  • I guess they're popular yeasts :P. Out of curiosity, has fermentation taken off now that you got it back up to 68F? If so, I'd bet it was just a temperature issue.
    – Gogeta70
    May 5, 2019 at 22:44
  • @Gogeta70 It's going again, but really slowly, a bubble maybe every 15-30 seconds, whereas 2 days ago it was bubbling every 2-3 seconds (it's only been fermenting for 3 days total). May 5, 2019 at 22:49
  • 1
    I my experience 3711 should always finish out pretty close to 1.002. How did you measure your gravity? If you used a refractometer, you have to compensate for alcohol, or they'll give you a high reading.
    – Frazbro
    May 23, 2019 at 22:25

2 Answers 2


I'd stay they got crashed out with the temp swings.

Bring them up to 68°F and rouse the yeast.

Chlorine gas a low boiling point and is all but gone after a few minutes above 96°F. Chloramine different animal, doesn't boil out. And will still work as a sanitizer to rid water of bacteria / fungus. Usually the pitch overwhelms the effectiveness of the sanitizer. Yes it usually just manifests as off flavors rather than stalled fermentaions.

The only other thing would be that it is at terminal gravity and the sugars left are just not fermentable or still starch. Typical of a very high mash temp 159+

  • 1
    Actually, I think that my thermometer was a bit off because it wasn't fully submerged. I mash on a gas stove and to maintain the temp I have the heat set super low. One day I came back after 30 minutes and it had climbed to 180F. So honestly this might be the actual issue, because I did get the fermentation back up to 70F and roused the yeast, but it never started up again. So it seems that not controlling the mash temp and letting it get too high is actually the cause! May 25, 2019 at 16:31

Temperature changes in fermenting is rarely a good thing.

For Safale US-05 the ideal range for fermenting is said to be 18-28°C (64-82°F), if the temperature drops to 45F in your fermenting space, it could very well stop the yeast activity.

I would advice to control temperature of your fermenting wort by putting a temperature controlled heater in order to stay in the correct temperature range for your yeast.

That being said, getting the temperature back up should restart your fermentation. Of course, the endured stress and temperature changes makes the yeast slower than if it didn't stall.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.