Temp Control: Air Temb Vs. Liquid Temp

After an extensive search and reading many threads on the matter, I'm still uncertain so I figured I'd consolidate it all here. I know a lot (if not most) of you control your fermentation temps one way or another, so what do you use air temp in the chamber or the liquid temp? Both? and... why? Ok, go!

i use the temp of the liquid wort. air is a poor conductor of heat. think about it when you pre-heat your oven to 350F everything inside the oven is 350F including the air but you don't get burned when you stick your hand in there.

The temp of the beer is what is important not the air. You don't need a thermowell. All you need to do is tape a temp probe to the outside of your carboy. Cover the prob with bubble wrap or some other material.

I use the beer temp by using a themowell by B3. I never trusted the taping probe to carboy method.

I filled my ferm bucket with water and taped a temp probe to the side as a test and after checking the actual water temp vs the probe taped to the side I found the difference was 1 degree.Tape it to the side and cover the probe with insulation and it`ll be fine.....+ 1 for measuring the temp of the beer though vs the air....because the fermentation will generate heat and you still want temp control over that.Measuring the air temp will cause more fluctuations.Listen to this episode of brewstrong....they cover this very issue really well

http://thebrewingnetwork.com/shows/533

I use a temp probe into the wort. That temp in the center of the wort can be different than that close to the outside as it is exposed to the cooler air around it. I also have a temp reading on my fermentation chamber so I get two readings, usually the air temp is 2-4 degrees cooler than the fermenting temp, esp. during active fermentation.

Bensiff said:

I use a temp probe into the wort. That temp in the center of the wort can be different than that close to the outside as it is exposed to the cooler air around it. I also have a temp reading on my fermentation chamber so I get two readings, usually the air temp is 2-4 degrees cooler than the fermenting temp, esp. during active fermentation.

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I concur...usually 3 degrees or so difference ambient to liquid.

I just tape the probe to the side about half way up.

If you submerge a glass carboy in a water bath then just measuring the water bath is fine. I've compared the water bath temp to the temp at the thermowell and they are always very close (this is how I keep ales cool). If the carboy is just sitting in air then you need to measure the liquid in the carboy. However, I measure the air temp in my lagerator and the beer temp with a thermowell and they are very close, but lagers ferment more slowly than ales (and thus put off less heat).

What kind of submersible thermometers are you guys using?

Right now I have a 1.075 OG beer in the midst of fermentation, ambient temp is 61 degrees, the temperature of the wort is 64 degrees. I genereally rule of thumb is that, if you pitch your yeast at close to ambient temp, the fermentation will be 3-6 degrees warmer than ambient I would say.