You don't need or want a seal while the beer is fermenting. That's why you use an airlock to vent the excess gas. You don't need a seal until you bottle or keg the beer and need to keep the CO2 inside the container.Jay, what options do you have for a thermowell in a carboy? Is the only option to use one of those orange "universal" carboy caps with the 2 holes? Those don't seal very well which is why I have never gotten a thermowell, but I'm interested to know if there's alternative methods.
This is what I currently do too, however it has it's flaws and is why I asked about the thermowell. Fermentation is an exothermic process, and thus the temp of your wort will be degrees higher than that of your gallon jug of water. I don't care about what temp the water is at - I want to keep the wort at a given temp.I have up to 3 carboys fermenting in a deep freezer at a time so a thermowell isn't practical. I have a 1 gallon jug filled with water that I drop the probe in and set temp to the low end of the recommended temp range. Trying to regulate the ambient temp will have the freezer running non stop and in short cycles which is tough on the compressor.