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Primary Fermentation Temperature Fluctuation

A newbie question here: In addition to keeping primary fermentation temps under a certain maximum, does it make any difference how much the temp fluctuates? As an example: Given a max temp of 68 degrees is there any difference between maintaining temps between 66-68 degrees vs. 61-68 degrees where the temp might continue to go up and down within that range?

The beer temp will depend on pitching temp, OG, ambient temp, etc… If you pitch in the low 60’s the beer should rise in temp as the yeast begins to ferment. If the ambient temp fluccuates then the beer temp will tend to follow but it also depends on how much exothermic energy the yeast produces. I like to use a fermentation control chamber to help reduce these fluctuations.

Thanks Bluesman. The reason I asked the question is because I am thinking about controlling the fermentation temp by placing the fermentation bucket in a larger bucket containing water and using freezer packs to lower the water temp as it rises from exothermic activity and replace the packs as needed. The downside of this technique would be causing the temp to fluctuate up and down during fermentation. BTW my ambient temp is 70 degrees so I’m not trying to get that much below ambient.

Having temp swing between 62 and 68 is much better than letting it get too hot. You can dampen the range of fluctuations by increasing the amount of water in the bucket that surrounds the fermentor (or using a bucket that holds a lot of water).

For my favorite ale yeast (WL001) I typically try to aim for the low end of the fermentation temperature range (60-62) during the early part of fermentation, and then let it increase rise to the upper end of the range as fermentation slows and finally stops.

Thanks Brewbeer; Good advice, starting at the low end will require fewer adjustments and better control. Haven’t decided between using WLP001 or Safale US-05 to brew partial mash SNPA clone.

Just be careful that you don’t let it get so cold that the yeast slow down or stop working all together. Some temperature fluctuation is pretty much unavoidable when you’re trying to control the fermentation temps, but the smaller the range of change the better.

Yes Yes when chilling the water bath don’t shoot for the bottom of the range until the ferment really gets going.

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