Hello. I keep my house chilly in summer (69 degrees). I brewed last Monday and pitched at 75 degrees and lidded up. My fermometer strip read 70 degrees and aggressive bubbling started the next day. The temp rose to 72 and overnight it read 74. My question is, how much heat is generated by the bio chemical reactions and how much can it heat the wort as compared to ambient air temps. Still new, only my third attempt. Should I be concerned about off flavors? Is 74 too high?
Actual fermentation temps
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worlddivides
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I've typically heard and read that an active fermentation can heat the fermenting beer up to 10 degrees warmer than the ambient temperature.
The fermentation range for ales is typically 60 to 76 degrees, but whether 74 degrees is too high will depend on the yeast strain you're using and the style of beer you're going for. Some yeast strains are optimal at 64, others at 68, others at 72, and others at 74 (some Belgian yeast strains are oftentimes intended for temperatures as high as 84 or 85 degrees, but even in those cases, they usually start out lower and slowly rise to that temperature). Yeasts almost always have their optimal temperature written on the vial (for liquid yeast) or the packet (for dry yeast).
The fermentation range for ales is typically 60 to 76 degrees, but whether 74 degrees is too high will depend on the yeast strain you're using and the style of beer you're going for. Some yeast strains are optimal at 64, others at 68, others at 72, and others at 74 (some Belgian yeast strains are oftentimes intended for temperatures as high as 84 or 85 degrees, but even in those cases, they usually start out lower and slowly rise to that temperature). Yeasts almost always have their optimal temperature written on the vial (for liquid yeast) or the packet (for dry yeast).
Thank you. The beer is a MO/Mosaic smash fermenting with WY1272. I will consult their site and see if it provides an optimum range. I also put the wet towel around the bucket under a box fan this morning and the temp has dropped to 68. Will the large temp swing have any undesirable effect?
The best thing I ever did for my beer was to ferment it at 68F internal temp. The temp on the side of the carboy is lower than the temp in center mass. That generally meant setting the ambient in my fermentation chamber to 66F during the first few days. 2-5F gradient between those two measurements is not uncommon for me during active fermentation, so if your fermometer strip reads 74F, your beer could really be at 78F if you have an especially vigorous fermentation going on.
The drop to 68° won't hurt the beer. However, it might not help with respect to reducing off flavors from high fermentation temps. It is most important to control the temperatures during the early and most active periods of fermentation, as that is where off flavors can be created.
74° is a little above the recommended range of 60° - 72° for 1272, and is likely to give you some fruity esters. Don't worry about it too much, you will still have a drinkable beer, but it might not be exactly what you wanted or expected. You might want to look into swamp coolers (basically a tub of water into which you can put the fermenter and blocks of ice) to keep the beer at the correct temperatures. The wet towel and fan can provide even more cooling when used with a swamp cooler.
Brew on
Please explain why there is a 2 to 5 degree gradient between the two measurements. You say 'vigorous' fermentation. When it s actively fermenting, there is so much mixing of the beer in the fermenter that the temperature is pretty uniform throughout. The only temp gradient is thru the wall of the fermenter, and since the liquid heat is more dominant than air, the temp strip will give you a pretty close reading to the actual beer temp. probably within a degree (accuracy of the strip aside).
I've not fermented in a carboy yet. My previous beers have been in a bucket so I'm not able to view the actual physical machinations of fermentation. Is there a lot of physical mixing of the baby beer? Enough to prevent cold / hot spots?
JINKS
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Check out this video I found on the tubes, I tend to stare at mine, its kind of mesmerizing.
[ame]https://www.youtube.com/watch?v=ua25L9KH6AM[/ame]
Since you are just beginning, look up a swamp cooler and use it for temp control. You can always use yeast that ferment at higher temps and work on your process. I used swamp coolers for many batches. Cheap and easy fermentation control. Pitching enough yeast is also key. If you pitch enough yeast the fermentation time is shortened, and more clean. Once you pitch and control your temps for the first 4-5 days, your in pretty good shape. Then if your batch warms it is OK. I have also experimented with water in my bucket. I covered the bucket with a box and a portion of my cooling floor vent. I could control my fermentation relatively well with this method as well. The swamp cooler was better, but the box and vent was better than nothing.
I've had it in a fashioned swamp cooler for the past 2 days and the temp is between 64 and 66 degrees steady now. Thanks for all the info. The resources available on here are truly amazing. Thanks again for forthcoming advice. Hope it turns out as good as it smells!!
JINKS
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Yea I was a little spooked the first time I saw it about 25 years ago. I didn't have internet to see if it was normal, so the first drink, of the finished beer, I was fully prepared to spit out.
DurtyChemist
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The beer will cool as it goes from the middle of the wort to the outside. Ask anyone who ferments a 10 gallon batch or bigger in 1 vessel what the temperature on the outside says vs what a thermowel says. You'll be surprised how much heat yeast generate when they're creating beer.
With all that said I just try and keep the outside of my wort under 70 since I don't have fermentation control. If I had fermentation control I'd drop a thermometer in the middle of the wort to monitor temps compared to what the fridge temp said.
The temp will be virtually the same throughout the beer due to the activity. I agree it will heat up relative to the air temp outside, but it is going to be pretty uniform inside the fermenter.
It gets kinda hot in the Sac valley so I bought a plastic trash can for $13 and a digital aquarium thermometer for $8. Put the carboy in the trash can and fill with water just above the wort level. Put the sensor in the water and let the thermometer hang out. Put the lid on it and add plastic blue ice blocks to regulate the temp.
Works very well
Works very well
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oops, wrong thread 
It's going to depend on the yeast, the ambient temperature, the geometry of the fermenter, and a bunch of other things, but as you can see from that video, you can generally count on it circulating pretty vigorously. Some yeasts are even more intense, especially some of the more thermophilic Belgian strains, some of which pretty much require a blow-off tube even when using a bucket (the tube goes in the airlock grommet, just as with a carboy). It takes a much more vigorous fermentation to do that, since there's no constriction at the top as there is with a carboy.
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Trouble with your post is that the person asking is brewing a five gallon batch in a bucket.
I've done the thermowell test with 5-1/2 gallons of wort. Like Calder said, there was virtually no difference between the temperature at the center and at the surface of my carboy throughout the fermentation. I doubt that 10 gallons would be that much different.
In my opinion, a thermowell in my carboy was an impressive looking piece of bling, but had little value to me beyond that.
Its been many years since I used those strips to measure temperature, but for me at least I did see a difference of a few degrees between what the strip read and what a SS thermowell down the stopper of the carboy read. I have always attributed it to the fact that the strips sit on the outside of the glass and glass is not highly thermally conductive. Using the thermowell was advice my LHBS gave me, and it really helped the quality of my beer back when I was using carboys. It may have only been a few degrees but it was a few degrees that mattered a whole lot for me.
It is entirely possible that part of the difference I saw was error in the strips vs the auber probe I used in the thermowell too. I cannot say I did a calibrated scientific study.
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