Fermentation temperature/ambient temperature

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Well-Known Member
Jan 3, 2008
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I've put together a simple insulated fermentation chamber that I have on the balcony. One of the reasons I built the box was to be able to ferment at a slightly lower temperature than I can do in my apartment (houses up here are insanely well insulated compared to US standards so there are no temperature gradients whatsoever indoors -it's 21-22C everywhere indoors...).

Now, I've set it for 19C (66F) for my ale that's fermenting in there. Out of curiosity I fitted a thermocouple in a way so I can measure the temperature of the wort/beer itself reasonably accurately during the fermentation and currently (30hrs since pitch) the fermentation temperature is 22C (72F) and the ambient is rock steady at 19C (so the yeast is certainly producing some heat).

So now for my question; is "suggested fermentation temperature" the ambient temperature, or is it the temperature of the wort during fermentation? Is there any good info on typical fermentation (wort) temperatures during the different stages of fermentation? At what temperatures are excessive esters and fusel alcohols starting to develop?



Well-Known Member
Nov 28, 2007
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somewhere special
A lot of this stuff you can find around the site here and at http://howtobrew.com. If your target temp is 66F then your wort/beer should be 66F. Try dropping the temp a bit, anything above 70F can cause some esters, but I'm not sure of the exact temps.

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