please explain to me how glass gets wet on the outside

some bongs i have i leave them sitting around, when i pick them up it seems they are slightly damp to the touch in certain areas on the outside after sitting around for a while. barely enough to even make a visible mark on a paper towel, but what gives?

lmao but why some bongs and not others

I don't really see a way to give a serious answer to this question without more information. My guess would be it's about the ammount and temperatur of water in certain pieces, the outside temperatur and whatever variables are left out.

Do the pieces that get damp have anything in common?
What are those "certain areas"?
Where is the glass stored?
What's the temperatur and humidity?
etc...

I had a tube from ClearCleanGlass that had a micro crack in the pinch that held the perc. It was barely noticeable but for the constantly damp foot. Filled the pinch with wax and it was good. I doubt that's the problem you have though.

It is, condensation. Sounds right.

Warm humid ( supersaturated ) air condense and collect on cooler surfaces in a phase change.......

Possibilities:

Thick glass, little water. NO?

Thin glass, fulla water => YEP?

ya they are all sitting right next to each other in a cabinet that is definitely a pretty consistent temperature and humidity, but glass thickness and amount of glass relative to water sitting inside of it varies a lot. i remember my old hydratube which had a thing for "sweating" a lot...