Attempting the swamp-cooler method to control fermentation temperature, I've logged some temperatures throughout the lag & primary phases, and I'd like to know if they are in the ballpark.
Below is a picture of my cooler.
I usually brew 2.5-3 gallon batches in a typical 5 gal batch bucket. So in the photo, the fermenter is filled to 2.5 gallons, which is right about at the cooler water level. Cooler water is mixed with StarSan. Not easy to see in the photo, but I also have a t-shirt draped on one side of the fermenter for wicking/evaporation.
My ambient basement temp = 72-24 deg. F
Pitched at 63 deg F.
Before posting a lot of temp data, I'd like to ask a question about how to interpret the stick on thermometer. From the above photo, the thermometer is vertical, the 63-61 deg cells are right at cooler water level (and also at wort level, approximately). Some thermometer cells submerged in the cooler water, and some completely above wort and cooler water.
After a few days of swapping bottles and taking readings at the water level, where 63-61 deg was indicated by the ferm, I noticed that a number of other cells on the thermometer were "lit", as shown above. I guess I expect this kind of thermometer to show a gradient in temperature if one exists (that is, more than one temperature, simultaneously), but now I question which values best represent the ferm temp ? In the photo, in case it is not clear, the values: 77,75...72,70,68...63, and 49,48,47, ... are lit up even if slightly.
When I logged ferm. temps., I was basically keying on the values at or above the cooler's water line, which in this case is the 63-61 deg mark. This also coincides with the top of my wort.
What my log seems to show is that the ferm. wanted to warm most aggressively in the first 24-36 hrs...seemed like bottle replacements were needed frequently to keep the ferm temp under 68-70...drops of new bottles would pull the temps back down to 63 or 61. After these 36 hours, ferm temp seemed to settle & be easily controlled around 63-61. But I see the other figures mentioned above too, so a little confused.