[Enthalpy]

Hello dear friends! 

I once put much table salt in tap water, more than could be dissolved, and forget it in a small polypropylene box (meant for photo film then) with a watertight plastic cap, head up, with the water filling maybe 2/3 of the height.

After about a year in a cupboard without movements and at temperate room temperature (with limited daily temperature cycles), salt had deposited on the outer side of the box near the cap on a regular pattern and in significant amount. Most water was still in the box. I'm no more sure if salt had deposited within the bow as well. I'm sure the boxe's outer side was dry and clean at the beginning, and the cap as well.

Dry salt in a box doesn't do that. 

My least bad explanation is that (...despite distillation serves to get sweet water) vapour can dissolve some salt. Not much, but definitely more than salt's negligible vapour pressure, and has helped salt to move to the joint, where dropping vapour concentration let the salt deposit. Though, I'm not really pleased with it, especially because of the amount of deposited salt.

Other explanations welcome! Denials, challenges, alternatives, comments... Thanks!

[Arkcon]

So you're seeing solid salt creep out past the seal of a container full of concentrated solution?  This is a known phenomena, some crystals nucleate on the inner surface, and function as a wick, allowing more solution to crystallize up further, until liquid escapes the seal, and and crystals seem to crawl out of the container.  I understand 'tho, usually creep happens more when a container is full.  But even a screw-cap seal, will allow crystalline creep, it doesn't have to be a film container lid.

[Enthalpy]

Thanks Arkcon!

When comparing the small amount of lost water and the significant amount of deposited salt, this would make more sense than vapour carrying the salt away.

Though, I saw no salt deposit at the inner wall, only past the lid.