Thanks John, that's really helpful. I actually stayed in the cave a good part of today under different scenarios, and just visually watched the fog pattern in the cave, as well as monitored the readouts on temp and RH...with and without the fabric sock, different humidifier placement - and you bet, your controller fans mounted on top of the UHs, to blow the fog up and over! The antagonism between the cooling cycle and the RH was dramatic...especially with the cooling piped "naked," just the elbow leading to what would be the duct, RH went from 92 to 83 in short order. It climbs back once the cooling kicks off, but it does take a few minutes. Your idea of a log is a great idea. One of my hygrometers has a min/max function, and I about flipped - as high as 67F and as low as 42....which makes no sense, as I know the temp is pretty spot on and the basement is well insulated. I'm hopeful that's a complete historical record, since the thing turned on, and not the last 24 hours...at any rate, thanks, that's a great idea.
So - my ignorance is showing - but how do they get such a perfect stream, as in that video? Pav had the thought that the place was likely exceedingly well insulated, if not fully subterranean, so cooling need is likely minimal (active system, but a very low cooling load). Makes perfect sense. That air flow and incredible, blue-smoke of humidity...man, it would be nice to know more how this is done. Any thoughts, yourself?