insulating temp probe against glass carboy

Somewhere's on here I got the idea to insulate the ferm chest freezer temp probe against the glass to get a more accurate temperature of the carboy.

This will be the 2nd batch I have done this way. The last one took longer to start fermenting than I would have liked. (I know there is a couple other variables, but mainly looking for input on this method).

I have a separate plastic cup full of water sitting next to the carboy that I placed in the chamber 2 hours ago. The temp of this cup is 45*F. I am shooting for 65*F fermentation temp. I know the glass of the carboy would take a while to chill, though perhaps the bottom is cooling the contents quicker than the side behind the insulation is getting chilled and dropping the yeast? My thermometer won't reach the liquid in the carboy to verify it's temperature.

Just looking for some opinions on this method of ferm temp control, thanks

You have a couple options. You can strap the probe to the carboy (or into a thermowell in the beer), and that will work great as long as your thermostat has a low differential, like 1f. Then it's set it and forget it.

But if you use a Johnson analog unit, or similar, with a differential of 3.5f, then that's not so ideal IMHO. There, a better solution is to leave the probe in the air, and let the mass of the beer maintain itself to within a degree or so. This requires you to manually tweak the thermostat daily during the first few days of fermentation. Kind of a pain. Then you monitor the beer temp with a stick on strip or measure directly. The strips are accurate within a degree or so.

They make probes that you can drop your probe in the heart of your carboy to get an absolute accurate reading of your fermentation.

As far as temperature stratisfication (****ing up spelling on that horribly, I'm drunk, **** off) set up a fan in the fermentation chamber and that will help.

I had some extra rigid poly insulation from my chamber build, so I ended up just cutting a cove profile into the insulation using my table saw, finding a profile that matched that of my carboys. I cut a little recess for my temp probe and used some nylon straps to secure the whole gimmick to the carboy. Cheap and works great.