Controlling Fermentation Temperature

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Bobby_M

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If you've ever heard people say how controlling your fermentation temps are a huge step to improving your beer, you've probably given it some thought. You may have also concluded that keeping the primary in an area with ambient temps in the general safe temp zone was good enough. Not really.

The first thing you ought to do is get some stick on thermometers to get a reasonable idea of what temp the wort is.

Fermentation kicks off a lot of heat so the wort is always going to be hotter than ambient during the active period. Just so you know I'm not just spouting off things that have been said in the past, here's proof.

This is my fermentation and cold conditioning fridge. On the top shelf you'll see some American Amber that is done with active ferment and has been transfered to secondary for aging and clearing.

On the bottom shelf is a Barleywine and ESB that are at peak fermentation "high krausen" having been pitched on yeast cakes two days ago.
fermfridge.jpg


Right, so what?
Here's what temp the Barleywine is running:
barleywinetemp.jpg


Here's the amber:
ambertemp.jpg


Yeah, the actively fermenting beers are 10F hotter. You might guess that it's because they're in different elevations in the fridge but think about it. Heat rises so if anything, the top beers would be warmer.

The moral of the story is that you can't assume that a reasonably comfortable ambient of 70-75F is anywhere close to cool enough for fermenting. Maybe you knew that. If not, this post is for you.
 
I will 2nd this. I have noticed a huge difference in how good my ale tastes between keeping it in ambient 70 degrees in the closet upstairs and the ambient 60 in my basement.
 
I also agree. I use a temp controller in my freezer and set it usually around 62F for ales. Sometimes I have to lower it more than that when it goes over 70F. I do, however raise it to around 65F when activity slows down.









Chris
 
I just finished my keezer for the most part and was thinking about doing a lager now, However that means that I cannot do any ales. My apt temp varies by 20 degrees easily over a few hours and although the basement stays at a nice 69 during the summer that is still a little hot considering all the heat that active fermentation throws. And this is why we have apfelwein!
 
my ale fermentation cabinet will be staying at a steady 56°F ambient temp, leaving the beers to go no higher than 65°F. can't wait to get that thing up and running, i'm almost finished with the door and then she's good to go!
 
I have a fridge with tepm control, but have been experimenting with keeping tepms. Is there a general range between beer temp. and ambient temp of the fridge? Is it 10 dgrees diff.? I thought at first that the two temps would match, NOT! The controller I have is a single stage, so I have put a small light bulp in the fridge and turn it on and then set the fridge to a colder temp than the desired ferm. temp. Is this how others are doing it?


Eastside
 
Bobby, I'm really glad you posted this. So many people worry about getting the right recipe or mash temperature or numerous other things, but a non-optimal fermentation can screw the pooch on what was up to that point a top notch beer. It is probably the biggest difference between making a good beer and making a great beer. Do you ever wonder how the guys that win all sorts of awards at competitions in multiple categories do it? Look at NHC and what you have to go through to win a category - beat out 20 to 30 beers at regionals then do it again against the best of the best in round two - yet some guys win multiple categories and it seems to defy the odds. These guys have very controlled fermentations. Jamil says it is the most important part of making beer and there is no way you can argue with his success.
 
Bobby, I'm really glad you posted this. So many people worry about getting the right recipe or mash temperature or numerous other things, but a non-optimal fermentation can screw the pooch on what was up to that point a top notch beer.
+1. Great post Bobby. The only beer I've ever totally f**ked up was my first, which fermented in a room that was about 72F. I thought that was fine, but hadn't taken into account the heat from fermentation. The beer stank of bananas and was kind of gross. So I second everything you and BB have said.
 
Bobby,
+3 (if that is possible) on this post, I used to use a small fridge to control the temp, when it busted I went back to swap cooling methods. I can tell you the difference was highly noticeable. Finally bought a new fridge and using the old POS as my fermenting chamber. I'm back to making good beer now and striving for great beer with all grain.

Side note, thanks for all your postings, they helped me a lot. I just wish I could fit four carboys in mine like yours. (jealousy rising).
 
Great post.

I'm using the icewater bath & towel trick for now, and there is indeed a 10-15 degree difference between the water and the beer. Thankfully, I've gotten the ice water to where I pretty much throw one big blue ice pack into the water twice a day and it keeps things nice and rather steady.
 
Whatever cooling method you use, as long as you're conscious of the wort temp you'll be ok.

I have the temp controller's probe rubberbanded to the barleywine better bottle with the temp set to 67F. In order to get the fermenting wort to that set temp, the ambient of the fridge stays a consistent 10F lower for at least the entire second day of active ferementation.

I got this upright freezer for $20 on Craigslist 2 years ago.
 
Bobby's results are not some freak event. Any brewer should count on actively fermenting wort coming in at 5-10F over ambient. That is a wide range when it comes to fermentation, and it depends on a whole boatload of factors (e.g., yeast, fermentability of wort, what else is in the fermenting fridge, air currents, and even the ambient temperature).

I don't know if fermentation temperature control is the most important part of brewing, but it certainly is no less important than any other part of the process.


TL
 
...I have the temp controller's probe rubberbanded to the barleywine better bottle with the temp set to 67F. In order to get the fermenting wort to that set temp, the ambient of the fridge stays a consistent 10F lower for at least the entire second day of active ferementation.
When you use the liquid temp to control the temp controller, doesn't that cause the actual liquid temp to fluctuate more? For example, if you set the temp controller to 67F and the liquid rises to or above that, the fridge kicks on and stays on until the liquid drops to 66F (using a 1F differential here), but the fridge had been running for quite awhile to cause that liquid temp change and is now very cold, so now the liquid overshoots and continues dropping for a few more degrees. Then as the liquid warms back up it gets to 67F again and the fridge kicks on, but it will take awhile to get it cold enough to drop the liquid temp, so the liquid overshoots in the warmer direction this time.
I'm not sure how big a fluctuation this is, but it seems that using the ambient air temp with a 1F differential would keep a more consistent temp. I haven't tested this yet as I just got mine set up not long ago.
Also, if you use the liquid temp of one of the beers, the other beers are being temp controlled by how active the one being monitored is.

I'm guessing all the above doesn't matter as long as I keep it cool enough for all the beers. ;)
 
When you use the liquid temp to control the temp controller, doesn't that cause the actual liquid temp to fluctuate more? For example, if you set the temp controller to 67F and the liquid rises to or above that, the fridge kicks on and stays on until the liquid drops to 66F (using a 1F differential here), but the fridge had been running for quite awhile to cause that liquid temp change and is now very cold, so now the liquid overshoots and continues dropping for a few more degrees. Then as the liquid warms back up it gets to 67F again and the fridge kicks on, but it will take awhile to get it cold enough to drop the liquid temp, so the liquid overshoots in the warmer direction this time.
I'm not sure how big a fluctuation this is, but it seems that using the ambient air temp with a 1F differential would keep a more consistent temp. I haven't tested this yet as I just got mine set up not long ago.
Also, if you use the liquid temp of one of the beers, the other beers are being temp controlled by how active the one being monitored is.

I'm guessing all the above doesn't matter as long as I keep it cool enough for all the beers. ;)

Actually, my point is exactly the opposite. If you put your probe in the open cabinet of the fridge you have to make some assumptions about what the fermenting wort will run at. If you guess 10F and you're right, no problem.

I like attaching the probe to the exterior of the carboy. It's more temp stable than the open air and represents the wort temp more closely. You would get those wild fluctuations you talk about if you had the probe in a thermowell deep in the core of the wort.
 
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