Negatives to letting carboy heat up and cool down a little during fermentation

benbrewing

Do folks think it's bad to have temps swing say from 50-70 here and there over weeks during fermentation in carboys? I am working with mead and cider only... I just don't have a super stable fermenting room...

hotbeer

I think it depends greatly on what you are wanting your beer to taste like.
Probably could have a great tasting beer if you controlled the temps to keep it fermenting at the lower temps. And with the same recipe, let it ferment at the temps it achieves on it's own and achieve a different flavor that may also be enjoyable.
Type of yeast and everything else might make a difference. If you want repeatability, then you have to control everything. But you might control that FV temp to be higher if you like that flavor in your beer better.
I typically let my beers coast from the ambient room temp of about 69°F (20°C) to where they max out at 74 - 76°F (23 - 24°C). I've mostly done ales and IPAs and am just starting into porters and stouts.
If I move to lagers then I'll probably be controlling the temps with something.

hotbeer

But re-reading your question, I don't think that's what you ask...
If your ambient temps are changing that much, then that might be an issue if they happen to fall too rapidly at the time the yeast is getting all set to do the bulk of the fermentation.
So I'd recommend you try to mitigate the ambient temp swings if you aren't using anything to control the actual temps in the FV.

benbrewing

ok thanks.. yeah i try to have them all on heat pads which seem to be the right temp - seedlings germination mats- a very stable 65-70 for the materials it seems..a little less if the room gets colder..

hotbeer

Many times on carboys I'd just tape a thick piece of insulating foam over a temperature probe to keep the probe firmly against the carboy. The wider the area covered by the foam, the better for getting a truer reading of the temp inside. A thermowell or if you wish to spend the bigger bucks on a Tilt or Rapt Pill hydrometer will also give you accurate internal temps.
Once you know what the internal is doing then you can better guess if the large swings in ambient temperature are an issue for your ferment.

Deadalus

That's what I use. Do you wrap them around the sides or just sit them on top. I use one regular rectangular mat around my carboys and that works just fine with a towel to block the light in my unheated basement in the winter. Also, the pads are temperature controlled. I could throw a blanket on top if needed but the basement stays mid 50s or higher and I don't remember needing one previously.

benbrewing

Good call - thanks much...!

Zambezi-Special

It depends very much on the yeast.
I put my fermenters in a cooler box or a non working fridge/freezer to prevent too much of a swing. I have done so for 2 years and the beers are quite acceptable.
Note as well that bigger volumes change slower than smaller.

hottpeper13

As far as temp swings go , why don't you set your shower to the desired temp then chill it 20* and see how you feel. Now imagine you are a single cell without a sweater to stay warm.

hotbeer

It's yeast dependent for sure.
If you don't have active temperature control, can you at least put the fermenter in a big tub of water? This will mitigate the temperature swings and keep it closer to the middle of your 50 - 70 deg range.