• We have a new forum and it needs your help! Homebrewing Deals is a forum to post whatever deals and specials you find that other homebrewers might value! Includes coupon layering, Craigslist finds, eBay finds, Amazon specials, etc.

Observations, thoughts, and questions on fermentation temperature

HomeBrewTalk.com - Beer, Wine, Mead, & Cider Brewing Discussion Community.

Help Support Homebrew Talk:

mcleanmj

Well-Known Member
Joined
Oct 8, 2012
Messages
45
Reaction score
3
Location
Halifax
Warning: this post is very long, for anyone interested.

I’ve recently started brewing again after a 6-year break (living abroad). This time around, I’m trying to learn more and improve my techniques. In the past I never adjusted water chemistry or actively controlled fermentation temperatures. I move and travel a lot for work, so I currently live in apartment. The ambient temperature where I ferment beers ranges 75-80 degrees F. I contemplated building a fermentation chamber out of an old freezer but instead opted for one of these:

https://tinyurl.com/y8drlawh

I live in Canada, so I actually got this one:

https://tinyurl.com/yavn5xfc

This thing is made for a conical fermenter, but works for buckets and carboys, and can actually hold two 6-gallon buckets. What you do is put frozen bottles of ice in the cooler and switch them every 12 hours or so. Its allegedly much more effective than a swamp cooler. According to the manufacturer one frozen 2-liter bottle will reduce the wort temperature 5 degrees below ambient (2.5-degree reduction for every 1 liter of ice). Spoiler - it does work really well.

For my first brew, I made a blonde ale with OG 1.062. I planned to ferment it at 66/67 degrees. The ambient room temperature was 75 degrees. I cooled the beer to 70 degrees, pitched the yeast, and put the wort in the cooler with one frozen 2-liter bottle and one frozen 1.5-liter bottle (aiming for a little less than a 10-degree reduction). Note - I monitor the wort temperature with both a stick-on thermometer and a probe thermometer insulated and taped to the fermenter. The beer cooled to 68, and actually continued dropping to 66 and all the way down to 64 by the next afternoon. I was pretty surprised. I switched the 2-liter bottle for a 1.5-liter bottle, wanting to maintain 66 degrees. The next morning the temperature was up to 68 and the airlock was bubbling vigorously. I wanted to keep it at 66, and I switched in fresh frozen bottles, but the temperature did not drop. I switched back to a 2-liter bottle, but still the temperature did not drop. The wort remained at 68 well into the next day with a ton of airlock activity. As the airlock activity slowed, the temperature cooled back to 65 degrees, but interestingly rose back to 68 the following day (no change in ambient temperature). From that point forward I was able to maintain a stable 68 degrees (in a 75 degree room) with only one 1-liter frozen bottle (pretty amazing).

The fermenter bag is clearly effective, but certainly takes some dialing in and continued manipulating to maintain a stable temperature. I was very surprised that for the 2nd and 3rd week of fermentation I could maintain a 7-degree reduction with only one 1-liter ice bottle.

I am currently fermenting a huge imperial stout. This thing came out at 1.118 OG. I used 3 packets of rehydrated Nottingham ale yeast hoping for a strong fermentation. My plan was to ferment it at 64 degrees for 4-5 days and then raise it to 68 degrees for the rest of primary fermentation. Ambient temperature is 78 degrees. I cooled the wort to 70 (best I can do with tap water), aerated it, pitched the yeast, and put the it in the cooler bag with one 2-liter bottle and two 1.5-liter bottles. Within 5 hours the wort had stabilized at 64 degrees. 7 hours post-pitch, I aerated the beer again (and saw a visible krausen already forming). 3 hours later (10 hours post pitch) the airlock was bubbling strongly. The temperature stayed stable at 64 degrees the entire day and evening. However, late night I noticed the temperature had risen to 66. I added an additional 1.5-liter ice bottle and a small ice pack. The temperature dropped back to 64. By 7:30 am the wort temperature has risen back to 66 degrees (while the ambient was 77). I switched all the bottles with fresh ones and added more ice. The total amount of ice at this point was 9 liters (theoretically enough to reduce 22 degrees below ambient), however some of the bottles were only partially frozen. By 8:00 am the temperature had actually increased to 68 and the airlock was going crazy. I added another 1.5-liter bottle, for a total of 10.5 liters of ice – theoretically enough for a 26-degree reduction, but the wort only chilled to 67! I then pointed a large fan with a bowl of cold at the fermenter bag, and the temperature dropped to 66. However, with all of that, I could not reduce the temperature to 64. I couldn’t add anymore ice, because I needed to save what I had remaining.

Altogether, I found this incredible. In a 77-degree room, with enough ice to reduce the temperature to the low 50s, I only managed to reduce to 66 degrees. This means that as the wort was approaching peak fermentation it was generating an incredible amount of heat!

To me this brings up a number of questions on fermentation temperature. When people say “I fermented my beer at 68 degrees” do they mean the room was 68 degrees, or the wort remained stable at 68 degrees? If you are fermenting a high gravity beer in a 68-degree room, the wort might be reaching 80 degrees! A friend of mine recently brewed an imperial stout with OG 1.2. He fermented it in a 72-degree room. His fermentation finished in 5 days with 75% attenuation. However, that beer likely skyrocketed into the 80s during peak fermentation.

For those of you with freezer-style fermentation chambers, do you actively monitor the wort temperature, or only the chamber temperature? If you monitor the wort temperature, do you have to reduce the chamber temperature during peak fermentation to maintain a stable wort temperature?

Anyway, that’s my huge story. It has me thinking, and definitely wondering how much wort temperature increases when fermenting in a cold room or basement. I found these related articles:

Fermenting in Air | Beer Fermentation Temperature

Temperature: Wort vs Room

Cheers
 

VikeMan

Well-Known Member
Joined
Aug 24, 2010
Messages
1,090
Reaction score
582
When people say “I fermented my beer at 68 degrees” do they mean the room was 68 degrees, or the wort remained stable at 68 degrees?
They mean wort temp, not ambient.

For those of you with freezer-style fermentation chambers, do you actively monitor the wort temperature, or only the chamber temperature?
I monitor both.

If you monitor the wort temperature, do you have to reduce the chamber temperature during peak fermentation to maintain a stable wort temperature?
Sometimes. But I try to leave enough buffer that it's not necessary. I also use a heat wrap around the fermenter for fine adjustment. So, 2 controllers.
 
OP
M

mcleanmj

Well-Known Member
Joined
Oct 8, 2012
Messages
45
Reaction score
3
Location
Halifax
They mean wort temp, not ambient.



I monitor both.



Sometimes. But I try to leave enough buffer that it's not necessary. I also use a heat wrap around the fermenter for fine adjustment. So, 2 controllers.
How much difference do you see between chamber temperature and wort temperature?
 

VikeMan

Well-Known Member
Joined
Aug 24, 2010
Messages
1,090
Reaction score
582
How much difference do you see between chamber temperature and wort temperature?
In my experience, It depends a lot on the gravity. Typical mid-gravity beers might be about 4-6 degrees F. A really big beer (e.g. imperial stout) may push 10 degrees F or so.
 
OP
M

mcleanmj

Well-Known Member
Joined
Oct 8, 2012
Messages
45
Reaction score
3
Location
Halifax
Wow, 10 degrees! That is amazing. I never appreciated how much heat a high gravity beer could generate. I'm quite happy with the beers I made in the past, including big stouts, but looking back on it they were fermented in a cold basement, so likely reached upper 70s at peak fermentation. Crazy.
 

VikeMan

Well-Known Member
Joined
Aug 24, 2010
Messages
1,090
Reaction score
582
Wow, 10 degrees! That is amazing. I never appreciated how much heat a high gravity beer could generate. I'm quite happy with the beers I made in the past, including big stouts, but looking back on it they were fermented in a cold basement, so likely reached upper 70s at peak fermentation. Crazy.
I should add that most of my experience is with 5-ish gallon batches. Smaller batches will show less difference between temperatures and larger batches will show more.
 

day_trippr

A bad time to be an empath.
Joined
May 31, 2011
Messages
32,303
Reaction score
13,200
Location
Stow, MA
Warning: this post is very long, for anyone interested.
It is indeed. I'm ok with it, but thanks for the warning ;)

[...]For those of you with freezer-style fermentation chambers, do you actively monitor the wort temperature, or only the chamber temperature? If you monitor the wort temperature, do you have to reduce the chamber temperature during peak fermentation to maintain a stable wort temperature?[...]
I don't - I have a BrewPi "minion" to do that for me. It keeps an eye on the wort temperature (and the ferm chamber air temperature) and controls the compressor (and heater if needed) automatically to keep the wort within a scoche of the target (Set Point). So right now I have ten gallons of 1.108 chocolate stout brewed today under control of a tiny Raspberry Pi computer that talks to an Arduino over Bluetooth to take care of my beer :)

1593574884471.png


Cheers!

edit/ps: the orange line reflects where the BrewPi algorithm wants to go. It will typically look like an amplified inversion of the beer temperature, so if the beer is trending warmer the orange line will turn negative, the steeper the former the steeper (in the opposite direction) the latter will be...
 
Last edited:
OP
M

mcleanmj

Well-Known Member
Joined
Oct 8, 2012
Messages
45
Reaction score
3
Location
Halifax
It is indeed. I'm ok with it, but thanks for the warning ;)



I don't - I have a BrewPi "minion" to do that for me. It keeps an eye on the wort temperature (and the ferm chamber air temperature) and controls the compressor (and heater if needed) automatically to keep the wort within a scoche of the target (Set Point). So right now I have ten gallons of 1.108 chocolate stout brewed today under control of a tiny Raspberry Pi computer that talks to an Arduino over Bluetooth to take care of my beer :)

View attachment 687469

Cheers!

edit/ps: the orange line reflects where the BrewPi algorithm wants to go. It will typically look like an amplified inversion of the beer temperature, so if the beer is trending warmer the orange line will turn negative, the steeper the former the steeper (in the opposite direction) the latter will be...
Oh man! This is amazing. Once I buy a house I will upgrade to this type of system. My dad loves to wire up all sorts of Raspberry Pi gizmos, I will solicit him for the job with promise of free beer.
 
OP
M

mcleanmj

Well-Known Member
Joined
Oct 8, 2012
Messages
45
Reaction score
3
Location
Halifax
Its the following day and fermentation is slowing. Whereas yesterday during peak fermentation I needed 10 liters of ice to maintain 66 degrees, today only 3 liters of ice dropped it to 65. Really amazing to see the temperature output and how much it changes in a few days.
 

BrewnWKopperKat

Well-Known Member
Joined
Oct 6, 2017
Messages
1,330
Reaction score
719
I should add that most of my experience is with 5-ish gallon batches. Smaller batches will show less difference between temperatures and larger batches will show more.
Recently with my smaller (12-pack-ish) test batches, I've revisited measuring fermentation temperature when fermenting at "ambient" temperature. Strain of yeast is a factor. Strains that ferment faster (for example, Nottingham) tend to raise the wort temperature higher that slower fermenting strains (for example, US-05).
 

Vale71

Well-Known Member
Joined
Nov 1, 2018
Messages
2,362
Reaction score
1,169
To me this brings up a number of questions on fermentation temperature. When people say “I fermented my beer at 68 degrees” do they mean the room was 68 degrees, or the wort remained stable at 68 degrees?
That's a question that only they can answer as it depends on their setup. If they're measuring the temperature in the wort and driving their cooling system based on that measurement than that's the temperature the beer actually fermented at. If they're just measuring ambient temperature in a fridge and driving it based on that temperature then the actual fermentation temperature is unknown and can only be guessed at.
 
Top