Internal vs. ambient fermenation temperature

[chirs]

I have read here that the internal temperature of the fermenting beer can be as much as 7º warmer than the ambient temperature. My fridge reads 63º and the stick on thermometer on my better bottle reads 68º. How accurate are those stick on thermometers?
I have the johnson analog thermostat, so unfortunately I dont think i can make use of one of those thermowell probe/stopper things to really control the fermenting temp.

 

[ArcaneXor]

The stick-on thermometers are reasonably accurate within a couple of degrees, in my experience.

You can adjust your fermentation profile by compensating for the produced heat, i.e. you'd start at, say, 63, then slowly drop the fridge temperature while the yeast is at peak activity, and bring it back up into the upper 60s to mid-70s as it slows down to maximize attenuation and speed up processing of fermentation by-products. Just watch the delta between fridge and fermenter temperature to guide you.

 

[Diablo]

Agree that they're reasonably accurate. I wouldn't stick one on my kid's forehead to take his temperature but they're accurate enough for brewing

 

[northernlad]

I was wondering if the stick-on therms are affected by cold transfer through the glass if put in a water bath?

 

[KillerKellers]

I have read here that the internal temperature of the fermenting beer can be as much as 7º warmer than the ambient temperature. My fridge reads 63º and the stick on thermometer on my better bottle reads 68º. How accurate are those stick on thermometers?
I have the johnson analog thermostat, so unfortunately I dont think i can make use of one of those thermowell probe/stopper things to really control the fermenting temp.

You could just tape the sensor to the side of your carboy, that would be more accurate then the ambient air temp..

 

[Cerpintine]

The stick-on thermometers are reasonably accurate within a couple of degrees, in my experience.

You can adjust your fermentation profile by compensating for the produced heat, i.e. you'd start at, say, 63, then slowly drop the fridge temperature while the yeast is at peak activity, and bring it back up into the upper 60s to mid-70s as it slows down to maximize attenuation and speed up processing of fermentation by-products. Just watch the delta between fridge and fermenter temperature to guide you.

This.

I do two at a time in my chest freezer and to compensate I go a few ° lower than desired--ie, if I want 65° I bring the controller down to say 62. In my experience the sticky is 1-3° off. And as ArcaneXor mentioned, you can bring the temp back up after peak, especially if you plan on bottling right out of the fridge/freezer. At these cooler temps sometimes the krausen or whatever doesn't feel like falling. I dry hopped an IPA and took it right out of the freezer to bottle-- needless to say much hop sediment was pulled that never fell. More recently doing a gravity test, the krausen from a scottish ale didn't feel like falling after two weeks. What I do now is leave at room temp for roughly a week before bottling.

 

[chirs]

This.

I dry hopped an IPA and took it right out of the freezer to bottle-- needless to say much hop sediment was pulled that never fell. More recently doing a gravity test, the krausen from a scottish ale didn't feel like falling after two weeks. What I do now is leave at room temp for roughly a week before bottling.

Thats a good idea. I didn't realize temperatures as high as 63-68 could prevent krausen or hops from sedimenting. I wonder why that is?

I believe the 1-3º difference with the controller and the actual fridge temp is the built in differential.

 

[Cerpintine]

Thats a good idea. I didn't realize temperatures as high as 63-68 could prevent krausen or hops from sedimenting. I wonder why that is?

I believe the 1-3º difference with the controller and the actual fridge temp is the built in differential.

The differential really has no effect, just as the manual states. At most, say if the sticky says 62 and is deep blue, it'll just rise up to an orange color. My 1-3° was taking temp readings whilst doing hydro samples. Also I keep a bunch of water bottles in there so the freezer doesn't cycle as much and they usually are 1-3° warmer.

As for the krausen, people have experienced that here at warmer temps--all I know is when I popped the lid open it was a very chilly 62° and the krausen developed a thick texture it seemed from being cold. Anything above 65° shoudn't present a problem. Again, YMMV.

 

[broadbill]

You could just tape the sensor to the side of your carboy, that would be more accurate then the ambient air temp..

+1 to this...short of a thermowell that would go directly into your beer, taping the probe to the side of the fermenter is the way to go. You already have a temp controller, IMO you aren't utilizing it fully if you just letting the probe hang free in the fridge and setting it a few degrees lower to account for heat generated by the fermenter (e.g. setting for 62 if you want 67).

In my experience, taping the probe to the side of the fermenter, covered with some bubblewrap will allow the temp controller to keep the temp of your beer plus/minus 1 degree or so. No guesswork, set it and forget it. It really is that easy; I could not believe how well it worked when I tried it the first time!

Good luck!

 

[Cerpintine]

I guess attaching it right to the fermenter is the best way to go, assuming what you're using can only do one at a time. B/c I can fit and do two, I have to let it dangle right in the center Besides, these couple ° difference is really negligible. We can all agree our yeast is very happy in the 60s! My chest has internal step on the left side which one of the pails has to sit on, and naturally the other one becomes a bit colder. I'd suggest you look up your yeast and see what the optimal temps are (ie, 65-70, etc). The one in the higher range goes on the step..

 

[chirs]

Great advice broadbill. Guess I forgot about the KISS rule.