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Fermenter Temp Control for New Brewer

Greetings all,

I just pitched my first batch 36 hours ago, and I think I might be having some problems with temperature regulation already. I used the ‘Caribou Slobber’ kit from this website, and everything on brewday seemed to go well. The only issue was that there was just over an hour between taking the wort off the boil and pitching the yeast. However, the beer was 68 degrees F when I pitched the yeast (Danstar Windsor Ale Dry Yeast), which I thought was pretty good. The kit instructions say the optimum temp for that yeast is 64-70 degrees F.

I kept the glass carboy in closet with 68 degree air temperature, with the cardboard cover over the carboy. The next morning, it had already started fermenting and seemed very active already, with the temperature risen to 71. In the evening (about 18 hours after pitching), the temperature had risen to 72, and there was a LOT of movement and activity in the carboy, with about 3 inches of foam on top. I decided to remove the cardboard cover and hope the 68 degree ambient air would cool it back down to 70 or so.

Then, we left to go drink some beers at a friend’s house. When we returned (27 hours into fermentation at this point), the temperature had risen to 76. Sludge on the glass indicated that the foam cap had come very close to a blowoff while we were gone, but then receded back down to a 5 or 6 inch cap of foam. The beer was swirling around like crazy, and bubbles were coming through the lock almost constantly. I was pretty worried that the yeast was going to burn out all of the sugars too quickly and make an off-taste. So, I put the glass carboy in a bathtub filled with 65 degree water before bed, hoping it would cool the beer down to about 66 or 67.

This morning (now 36 hours after pitching), I found the beer cooled down to 66 as I had expected. However, the fermentation has slowed almost to a standstill now. The difference has been (figuratively and literally) night and day overnight. Small bubbles now only come through the airlock once every 6 seconds or so, and the foam cap has died down to just a very thin (1/8 inch) layer. The beer doesn’t seem to have much movement or activity at all inside.

First of all, is this a big problem, and should I be worried that this will be a bad batch? Second of all, what did I do wrong? Is there anything else I should do to try and make the best of the situation? I put the fermenter back in the 68 degree closet, with the cardboard over it again.

As a side question, is it ok that when moving the carboy, the beer was sloshed around quite a bit inside, and the foam cap was disturbed?

Thank you for reading this excessively long post. I appreciate any help I can get!

76°F is awfully warm, but I doubt it will be “bad”. Fermenting too warm will likely produce some fruity esters and “hot” fusel alcohols that you probably don’t want. Being your first batch, you probably also under-pitched the yeast, which would compound the problem. Fermentation is almost finished at this point, but I’d give the beer another week or so on the yeast so that they can “clean up” as much as possible.

Next time, remember that on average, the fermenting beer will be ~5°F warmer than the surrounding air. For most ales, a 65°F water bath would be ideal, and the fermenter can spend the whole time in there.

That isn’t a problem. As you noticed, fermentation is going to agitate things more than you ever could.

I don’t think you did anything wrong other than misjudge the increase in temperature that is caused by fermentation. Obviously, you could have done the cold-water bath sooner to avoid the big spike in temp, but these things are not that easy to judge and vary with yeast strain, wort fermentability, airflow and many other factors.

I’ve never used Nottingham, but generally an excessively warm fermentation will produce esters and fusels that are not desirable in most styles, but I doubt very seriously that your beer is ruined or undrinkable. I think the Caribou Slobber recipe is pretty forgiving (in other words there is enough complexity to the malt and hops to help mask minor flaws).

When the temp dropped from the cool water bath, the beer is able to hold more CO2 so some of the slowing in airlock activity may be attributed to this. You may even see an increase in activity once the temp stabilizes.

Let it finish fermenting in the 66-68 range, relax and have a homebrew, and see what happens. Chances are it will be fine.

By the way, the distubance and dropping of the Krausen (foam cap) is completely normal and not a problem.

Thanks for the replies, I feel a bit better about this. I suppose I can live with a bit of fruity off-flavor in my first batch, as long as I’m able to learn from it. Also, glad to hear that disturbing the krausen isn’t a problem.

What exactly does under-pitched mean? Does it just mean that I likely put too little yeast in?

Right, although I didn’t notice you were using dry yeast at first. One packet of (rehydrated) dry yeast is about right for an average-gravity ale. With liquid yeast, it’s better to use 2+ packs, or make a starter.

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