Fermintation question...

[SmartyJones]

So I'm only on day two of my beer sitting in my main carboy to ferment and I know temperature is a big factor, my question is this what happens if the temp fluctuates during this process? I am trying or wanting to keep it between 69-72 degrees but this morning it was up to 75/76 ... And when I got home from work it was down to 66 ... I'm going to have to figure something out with temp control... Will it mess it up with the changing temps?

 

[user 108580]

Is that the temperature of the air in your house, or is that the temperature of the Fermenting Wort?

 

[unionrdr]

I've had fermentations stall a bit & start settling with temp fluctuations like that. You def need to get the temps at least a bit more stable than they are now. I've even used a wet tee shirt & fan to keep temps in check by a few degrees.

 

[RainyDay]

I dont have much say in my apartment's temp in the summer (no A/C here in Seattle), so it'll vary. In the past it's never been an issue, although you can get off flavors such as esters if it gets too hot for too long. I currently have my carboy fermenting in a big rubbermaid container with about 6-8" of water, and i put some frozen waterbottles (full obviously...) in there to keep the temp down, and a wet towel over the carboy (soaked in the water so it acts as a wick). Right now i've got it hovering around 66º, which is good enough considering. Dirt cheap swamp cooler.

 

[microbusbrewery]

Yeah, for the best chance at making a great brew you really want to avoid big temp swings as much as possible. The amount impact can depend on the yeast you're using, but generally speaking, yeast will become more active as the temp increases. They also tend to have a bigger impact on the finished beer flavor the warmer they get (e.g. increased ester production). You can also develop fusel alcohols when the temp is too high too.

On the other hand, cooler temps tend make them want to go to sleep. Fermenting at the cooler end of a yeast's recommended range wil usually result in a "cleaner" fermentation with less of an impact on the finished beer flavor. If the temp is going up and down daily, the yeast will likely be more stressed than if it was stable, but that doesn't necessarily mean you won't be able to make good beer.

If you don't want to invest in a temp controlled ferm chamber at this point, try to ferment somewhere where the temp doesn't change as much (different room, closet, etc.). You could also try something to add thermal mass. For example, get one of those big totes with the rope handles at Walleyworld, fill it with water (at the temp you want to ferment at) then submerge your carboy in the water. The additional thermal mass of the water should help minimize temp swings a bit.

 

[Onlooker]

If you're referring to the temp in the house, then it's not likely that the wort is fluctuating quite that badly. It takes a while for a liquid to change temp. With that in mind, if you put it in a big tub of water you can keep it more stable by increasing the total liquid (edit: thermal, as microbus put it) mass. Even if you don't have to actually cool it down (which sounds like your situation) it will help temp control.

 

[FATC1TY]

If you don't want to invest in a temp controlled ferm chamber at this point, try to ferment somewhere where the temp doesn't change as much (different room, closet, etc.). You could also try something to add thermal mass. For example, get one of those big totes with the rope handles at Walleyworld, fill it with water (at the temp you want to ferment at) then submerge your carboy in the water. The additional thermal mass of the water should help minimize temp swings a bit.

This is the easiest way honestly. I'm doing this right now, since I turned my fermentation freezer, into a keezer at the moment.

Bucket in spare bathroom tub, filled to 5 gal mark with water and ice added daily. I have healthy fermentation going on, and the temp is reading, right at 64* for my yeast I'm using. The wort has little choice but to be pretty close to that temp, although it'll be slightly warmer during the violent fermentation, it'll be held in check and pretty darn close.