I finally want to start measuring fermentation temperature more accurately. I currently use a swamp cooler as my fermentation chamber, measure the water temp, and tack on 5-8 degrees as my assumed internal carboy temperature for the first 4-5 days. My blow-off valve gets a lot of use. Has anyone here built a thermowell - blow-off valve combo? I was thinking of just drilling a hole through the rubber stopper, putting a 12"-15" SS rod through it, and sealing the top and bottom of it with silicone. Does that seem like it'll work?