So I’ve got this Kolsch fermenting in the basement, where it’s about 66-68 degrees ambient, and I want to keep it colder than that, so I have it sitting in a cooler with enough water to go about a third of the way up the carboy.
Since I’m an idiot, I got some of my fermometers wet and ruined them, and ordered a new batch, which I placed on the fermenters up higher where I’m not going to get them wet sitting the carboy in a water bath. However, the lower, wet fermometer strip on the Kolsch isn’t yet destroyed, and so I have two working fermometer strips on the carboy and, wow do they show different temps. (This is a five gallon better bottle.)
The lower one, which is in contact with the chilled water (I rotate in milk jugs full of frozen water) reads about 48-50 degrees. The top one, high and dry, reads 62-4. I think, “that can’t be right,” so I sanitize a long, skinny candy thermometer I’ve got that will slip right through the bung port in the top to see.
Result: up high, the temp reads 62 degrees. Down low, the beer reads 56. The chilled water itself reads 42.
So there it is, a major difference in the temp in a couple of temperature strata. I figure the lower strip reads lower than the internal temp because, duh, it’s in contact not only with the bottle but with the colder ice water outside. But I’m really surprised by the difference in the readings inside. I guess maybe I shouldn’t be, given the heat rising thing. But I guess I need to fill that water bath up a bit higher if I want to keep more of the carboy cold.
Not so much a question as an observation that might help others out.