Second Batch, Temperature Variation, Re-started Fermentation

[tragic8ball]

Three weeks ago I bucketed my second batch of Palmer's Cincinnati Pale Ale recipe. Since I was never able to find a place in the house that stay below 70 degrees. I decided to place the fermentation bucket in a large tub and let it sit in a water bath to keep the temperature low. I swapped out ice bottles twice a day, and was able to keep it in the 64-66 range.

The airlock activity started vigorously, like it does, and then almost completely stopped within 72 hours.

It's three weeks later, I planned on bottling today, and I just realized that I've forgotten to swap out the ice bottles for the past couple days. The temperature is a steady 68 degrees, and now the airlock is bubbling about once a minute! Has the 2-to-4-degree warmer temperature woken up some dormant yeast? Is this good, or is it in the process of producing some nasty esters?

Obviously the desired temperature range is a constant, but that's hard to keep without some refrigeration+temp controller setup. Realistically, what is the allowable temperature variation for a beginner like myself?

I have a hydrometer and a OG reading from three weeks ago. I'll take it and let you know what I find out. In the meantime, can anyone confirm my suspicion about the temperature range?

 

[rsquared]

Air expands as it warms up, and contracts as it cools. What you're seeing from the airlock is almost certainly due to the warmer air expanding inside the fermenter and pushing it's way out the airlock. RDWHAHB!

 

[BigB]

First off, the airlock is not a fermentation gauge. It is merely one-way valve to allow excess CO2 escape. A minute change in temperature change 3 weeks into the process would likely have nil effect on the beer. Futher, the temperature range will vary with the recipe and the yeast. However, you can get away with a substantial temperature change and still have great beer. Most fermentation is done within the first week (this is where you need to be careful about temperature). After the bulk of fermentation is complete the yeast will "clean up after themselves" if you will. This stage lasts a couple weeks. Temperature isn't that critical at this stage.

The sudden minimal airlock activity is probably just CO2 coming out of solution. Very normal- especially if you move it or there is a temperature change.

 

[Yooper]

Is the SG changing? If it is, it's not done. If it's not, it's done. It's that simple, really.

As was mentioned, air locks can bubble for many reasons- fermentation, air temperature changes, moving the fermenter, even barometric pressure changes. If you take an SG today, and then again in three days, and it's the same, it's done.