Natural Temp Drop When Fermentation Slows Down

[Evan!]

My fermentation/aging room is around 58f these days. IMHO, perfect for fermentation, because the natural heat generated by the fermentation process brings the wort temp up to 62-63f.

Case in point was my cherry stout. I pitched at about 60f, and several hours later, fermentation was vigorous...the temps had risen several degrees. This was the Wyeast London ESB strain, which finishes VERY quickly...so, even though I pitched on Sunday afternoon, it's already slowing down today (Tuesday). At the same time, since the airlock activity has slowed down, the bucket temp has also dropped, back to about 58f. I have a heating pad and blanket ready...I'm just wondering if I should raise the temps back up to the low 60's until fermentation is done. My worry is that, without the heat from the vigorous part of fermentation, the temps will drop too much and cut fermentation short. Is this possible? How low do you have to go for that to happen? The listed range is 64-72f. If it sits around 58-59, is it going to stop things prematurely?

 

[cweston]

I usually try to shoot for the low end of the listed temp range: I think what would be ideal would be an ambient temp at or a degree below the lower end of the range.

I'd be worried about poor attenuation at the temps you listed, although I don't know from personal experience or anything.

 

[Torchiest]

I'm not the most experienced brewer here, but I'd say, yes, use the blanket, and keep it out of the fifties. What you're describing is exactly what happened to my oatmeal stout I just bottled last week. It got really cold in my apartment, and at one point my primary got down to about 59º. Fermentation pretty much stopped. I did get it up to around 64º again and SG dropped a few more points, but it's possible it stunted the completion. Of course, the beer still tastes great, so no disaster, but I think it's best to try to keep in it the sweet spot as much as possible. I was using White Labs London Ale btw.

 

[david_42]

No matter how vigorous a ferment runs, when it starts to run down it's a good idea to keep it in the ideal range. Those last few points are the hardest sugars to ferment & the yeast need all the help they can get. Many times, I end up raising the temperature to the high end of the range to let the yeast finish the batch.

 

[Evan!]

Thanks for the input. Just went home during my lunchbreak and put the heating pad on it. Hopefully that will bring it up from 58f in time for the yeast to finish.