I did my first brew 2 days ago, and I’m quickly learning that controlling fermentation temperature is not necessarily as easy as I expected it to be. I’m storing my carboy in an unfinished/unheated (but insulated) room that has been in the mid-60’s F for the last couple of weeks. My wort was 65 F when I pitched (Danstar Windsor yeast 64-70 F optimum temp).
12 hours after pitching, the fermometer on the outside of my glass carboy had risen to 68F. Lots of active fermentation.
24 hours after pitching, the fermometer was at 72 F and decided I would need to do something to bring down the temp. I made a swamp cooler for it.
36 hours after pitching and 12 hours in the swamp cooler, the fermometer was back down to 68F. I go to sleep, check on it 7 hours later, and the fermometer is down to 60F, and there’s much less fermentation activity. Thinking that 60 is too low, I pulled the towel off it and turned off the fan before leaving for work this morning.
A few questions for the more experienced brewers here…
How will temp swings like this effect the the finished product?
Is there a danger of the yeast dying when it’s down at or maybe below 60F?
How accurate are the Fermometers? I’m guessing the liquid inside might actually be a couple of degrees higher than the Fermometer reading, but wondering if anyone has tested.
How will temp swings like this effect the the finished product?
-You should be fine. It’s not ideal, but at least you didn’t get too hot.
Is there a danger of the yeast dying when it’s down at or maybe below 60F?
-It doesn’t die when it gets cold, it just goes to sleep. They die at high temps. They would have to be colder than 60 to sleep.
How accurate are the Fermometers? I’m guessing the liquid inside might actually be a couple of degrees higher than the Fermometer reading, but wondering if anyone has tested.
-They are pretty accurate (accurate enough).
You can use the swamp cooler filled with as much water as you can and not worry about towels, or ice. If you’re ambient temps are in the mid 60’s, the volume of water will help keep the swings minimal. The water will absorb heat from fermentation. If you want to keep it a bit cooler, add ice. You’ll learn how much ice will drop the temps.
Like you said, now that I got the ferm temp back down into the 60’s, I think I’ll be ok with just filling the tub with water and using that to manage temperature fluctuation (instead of using the tub + towel + fan). Hopefully I see active fermentation again when I get home from work…there was basically no bubbling in my airlock when it was down at 60F this morning.
I use a swamp cooler without a towel or fan in my unfinished storage room. My beers stay a consistent 64-66 year round. Ambient air temp is about 65-68.
They’re quite accurate. There was a thread on here a while ago where someone posted a link to test results on the accuracy of these.
Basically, when the ambient air temp and the beer temp are within a few degrees, the fermometer is dead on.
When the air temp and the beer temp start to get too far apart, that’s when the temp differences started to show.
For example, if you’re using a swamp cooler to hold temp at 65 in a room that’s 85 degrees, you’re temp will read higher then it really is by a few degrees.
If the wet towel was covering the fermostrip, the thermostrip was probably cooled 2° to 4° cooler than the wort. I leave the thermostrip uncovered and on the lee side from the fan.
