Are only quick temp swings bad?

[rtockst]

I left my house for a coulpe days over the weekend to go hunting, and the heating element in my furnace is broke, so I had no heat! My brew has been fermenting for two weeks, OG 1.07, and it is still F'ing fermenting because the temps have been so low in here. It started around 65, then went up to about 68, then down to 63, then down to about 58, then back up to 61. I know this wouldn't be good if it were a quick temp change, but those changes happened over the two week span (except for the 63 to 58 happened over 2 days). So I was wondering if this kind of temperature swing is bad in any case, or if it's just bad when it happens quickly? I'm not too worried, but I would like to know for future reference. What are the effects of this happening?

 

[Zymurgrafi]

Fluctuations are to be avoided for best fermentation. That said, the most critical time is the initial vigorous fermentation during the first few days. That is when it is best to keep the yeast stable. The temperature increase you mentioned from 65F to 68F was likely caused by the yeast and fermentation itself. It is an exothermic process so the fermenter depending on the yeast, the volume etc. can get anywhere from a few degrees to 10 degrees warmer than the ambient temp.


The drop in temperature you saw was likely when the initial fermentation was subsiding. The yeast were no longer as active and thus not creating as much heat so the fermenter began to cool towards the ambient temperature.

One simple way to help maintain a more constant temperature is to place the fermenter in a tub of water. The water will change temperature much more slowly than the air thus buffering any fluctuations.

 

[bull8042]

I won't try to give you a definitive answer as I am not sure. From what I have heard and experienced though, it is high temps especially during the first 12 hours or so will have the most negative impact on the finished beer.
Low temps will make the yeast sluggish and possibly cause early floculation and extended fermentation times.
I would say get the temp back into the proper range and let it finish. You should be fine.

 

[rtockst]

thanks guys. yea I thought the first 10 or so hours of fermentation were important. I can tell it's really slowing down my fermentation. Hopefully the gradual change wasn't enough to shock the yeasties or anything. One thing I'm worried about, is that you get more fruity and estery flavors at higher ferm temps. The recipe called for a 70 F fermentation where mine was mostly alot lower. So hopefully it doesn't turn out too smooth. I like those damn fruits and esters!

 

[histo320]

When i fermented my IPA it fluctuted between 65-and 72 (cold spell day after fermentation), I have noticed that it seemed to make it a very crisp beer. IS there any truth to that?