Inside/Outside Fermenter Temperature Question

[Lodovico]

Hello,

After a discussion with a brewing buddy last night, we were discussing fermentation temperatures and the fact that the process is exothermic.

He was saying that in a 5 gallon batch in a plastic bucket the temperature inside the bucket isn't going to be more than 2 degrees different than what the crystal thermometer is reading on the outside of the bucket.

Is this true? I know I've read on here that some people say it's as much as a 10 degree difference. He's claiming that because it's 5.5 gallons that it isn't going to be a huge difference and I would like to get a real scientific answer to this. I realize it depends on the yeast and other factors but I guess I'm looking for a realistic range.

I've had some beers that read 68 on the outside of the bucket and I wonder how warm things could potentially be on the inside. Anyone have some data?

 

[chicagobrew]

No data, but it wouldn't be that hard to collect. I monitor temps in the bucket using a thermowell through a stopper. One would just have to compare that to the readings on the outside of the bucket. Unfortunately, I threw out that crystal thermometer long ago so I can't help.

If you've ever watched primary fermentation in a glass carboy you know that there is a lot of movement going on in there. My guess would be that there's enough mixing that there is little temp difference between the inside and outside of the bucket. Maybe when fermentation slows down the gradient would get larger. I don't know.

 

[Ki-ri-n]

Check out this thread: https://www.homebrewtalk.com/f51/show-us-all-your-fermentation-closets-chambers-here-118479/index8.html

I just happened to see that post and remembered yours

02fx4dude is using a PLC to monitor temps (outside of carboy, inside and air temp). On/In temps are within 0.6* while ambient is almost 10* cooler.

 

[maida7]

the temp of the outside surface of the fermenter will be VERY close to the internal temp of the fermenting liquid.

UNLESS

The fermenter is placed in a very cold or very hot place. Like if you take a 70F fermenter and stick it in a 32F freezer. The outside skin of the fermenter will suddenly be much colder then the liquids inside. Eventually it will all equal out but temporarily there will be a vast difference between the number on the crystal thermometer and the actual temp of the liquid inside.

Does that make sense?

 

[chipotlemonger]

Bumping this thread. I have a temperature controller reading 64 on the outside of a 5 gallon plastic bucket. Fermenting a beer with OG of 1.051 using Wyeast 1968 London ESB. Figured I was still getting about 66 on the inside, but wanted to see if anyone else thought differently or had input.

Brewed 4 days ago, was going to move the bucket inside later today to bump its temperature up for the extended end of fermentation and diacetyl rest that I see mentioned so much with this strain!

 

[VikeMan]

Bumping this thread. I have a temperature controller reading 64 on the outside of a 5 gallon plastic bucket. Fermenting a beer with OG of 1.051 using Wyeast 1968 London ESB. Figured I was still getting about 66 on the inside, but wanted to see if anyone else thought differently or had input.

Any thermometer/probe attached to the outside of a fermenter will be influenced by both the wort/beer temp and the ambient temp.

Without actually measuring the wort/beer temperature, it's impossible to say what the delta is. It will generally be larger during the most active fermentation than at other times (assuming you're not actively cooling the beer from the inside).

That said, lots of people seem to get along fine by assuming 0, 1, or 2 degrees difference.

 

[day_trippr]

fwiw, I did extensive testing comparing temperature readings from a thermowell'd sensor in the dead center of a 6.5 gallon carboy vs a sensor strapped to the middle of the sidewall under an inch thick pad of closed cell foam. Throughout entire fermentations from pitch to the end of cold-crashing they never differed by more than 1°F. I can't say how a plastic bucket would perform but it shouldn't be a whole lot different...

Cheers!

 

[chipotlemonger]

Thanks for the input. Went ahead and moved it a day before intended to warmer temps inside. FWIW when I opened the fridge, it felt warmer inside than the ambient air temp outside at the time (which was expected, but still nice to actually confirm!). I just didn't trust it to remain that way through slower, less-active fermentation.