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Old 11-01-2011, 02:15 PM   #1
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Default Fermentation Temp - Ambient or Wort Temp?

I've seen a few discussions where it was difficult to tell if the fermentation temperature being referred to is the temperature of the wort, or the ambient temperature of the surrounding air. Generally, I refer to the wort temp, and I believe the fermentation temperatures recommended for different strains of yeast does as well, but I'm wondering what others practice.

One example is where a person says they're fermenting an ale at 60*. While it's possible, this generally seems lower than you would want most ales to ferment at. If they are referring to the ambient temp, then the wort would be around 65*, which seems more reasonable. I'd be worried if someone says they're fermenting at 72* ambient temperature, not realizing the wort will be at least a few degrees hotter, which could result in more ester production.

I guess it also depends on where the temperature probe is placed. I tend to not trust the sticker thermometers as much, so I stick the probe to the side of the carboy, insulating it from the surrounding air temps. I also keep a thermometer that measures the ambient temp, just to make sure.

I think I'm right in measuring the wort temp, but I haven't found anything specific. So if I'm wrong, please correct me.

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Old 11-01-2011, 02:43 PM   #2
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IMO Fermentation temps should always be measured as the temperature inside the fermentation vessel. That is what the yeast mfg. refer to and that is what the recipes in books/magazines refer to. Whether you are getting that temperature using a probe in a thermowell, a stick on thermometer or a probe taped and insulated to the outside of the vessel is up to you. If you are referring to the ambient air temp, then you really have no idea what your fermentation temperature is.
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