Ferment temp ambient vs. fermentation vessel

[Heavywalker]

What kind of difference is there between the ambient temp and the temp of the fermenting beer? I know that the yeast will make there own heat so I am wondering what a good rule of thumb would be for hitting the proper temp in the FV.

I am currently fermenting an IPA with WLP001 yeast, which recommends temps between 68-73 F. I have the carboy setting in the bathtub with water about halfway up the vessel, and a wet t-shirt covering the carboy. The highest that the water in the tub has got is 64F and the inside air temp is right at 70F. Any estimates on how much different the temp of the beer is compared to the water? I currently don't have a good way to measure the temperature of the carboy, it is one of the things I overlooked when starting brewing beer.

Thanks!

 

[homebrewdad]

During active fermentation, you can figure on the beer being 5-10 degrees warmer than the surrounding air temp.

Using water to regulate will be very helpful - the difference ought to be less.

 

[beergolf]

It depends. I find that if you are at the low end of the recommended temp range then it may only be a few degrees. If you are at the high end of the temp range for that yeast then it can be 10 degree or more over ambient.

 

[paraordnance]

I been monitoring surrounding water temperature and fermenting wort (thermowell) and the difference is usually no more than 2F from my observation (higher - thermowell). Water has a lot more thermal mass than air. You did a good thing submerging your carboy. Just monitor temp of surrounding water with ice bottles and you will be good.

 

[Heavywalker]

I been monitoring surrounding water temperature and fermenting wort (thermowell) and the difference is usually no more than 2F from my observation (higher - thermowell). Water has a lot more thermal mass than air. You did a good thing submerging your carboy. Just monitor temp of surrounding water with ice bottles and you will be good.

Great info, thanks! I knew someone would have done this experiment.