Lately I have been trying to nail down my fermentation temperatures. I have noticed that the temperature of my glass carboy varies 3-4º F from the top to the bottom, as measured by an infrared thermometer. Once the fermentation gets going everything is stirred up enough that the variation quickly diminishes to pretty much nothing.
I get pretty good correspondence from the IR to a 12 partial immersion lab type thermometer lowered into the wort at different depths. Theres a certain amount of guesswork, as I have to reel the analog out to get a reading on the lower depths. I am however satisfied that the IR is giving me a good indication. It could be a degree or so off of the absolute temperature, but the relative temps should be really good.
My tapwater temperature is in the high 80's, so I have been using a lot of ice with the carboy in the good old rope handle tub. Once I put the carboy in the tub with cold water, I obviously cant use the IR to measure the bottom temperature.
Last batch I apparently used too much ice, as it took 48 hours to start off with an active yeast slurry (S-05). Problem is, while the yeast were napping, the IR was telling me the temperature at the top was a balmy 70º F. The ice water in the tub was being held at 65º F.
I can understand its colder in the basement than the attic, but wow, thats a lot. I also fully appreciate that the delta T is going to be bigger with cold water on the bottom of the tub and warm air at the top.
My question (finally, right?) is; How should I regulate the temperature pre-fermentation? It appears the yeast are napping in the basement. When it warms up a little they take over the house and party.
To put it another way, if I want to pitch at, say 65 º F, where (and how) should I measure this?
I get pretty good correspondence from the IR to a 12 partial immersion lab type thermometer lowered into the wort at different depths. Theres a certain amount of guesswork, as I have to reel the analog out to get a reading on the lower depths. I am however satisfied that the IR is giving me a good indication. It could be a degree or so off of the absolute temperature, but the relative temps should be really good.
My tapwater temperature is in the high 80's, so I have been using a lot of ice with the carboy in the good old rope handle tub. Once I put the carboy in the tub with cold water, I obviously cant use the IR to measure the bottom temperature.
Last batch I apparently used too much ice, as it took 48 hours to start off with an active yeast slurry (S-05). Problem is, while the yeast were napping, the IR was telling me the temperature at the top was a balmy 70º F. The ice water in the tub was being held at 65º F.
I can understand its colder in the basement than the attic, but wow, thats a lot. I also fully appreciate that the delta T is going to be bigger with cold water on the bottom of the tub and warm air at the top.
My question (finally, right?) is; How should I regulate the temperature pre-fermentation? It appears the yeast are napping in the basement. When it warms up a little they take over the house and party.
To put it another way, if I want to pitch at, say 65 º F, where (and how) should I measure this?