Should I store greasy tires separately? Should I store my "greasy" tires separately from the ones that don't seem to sweat? 

I'm hand-washing and sorting my bricks from a big, uncovered tub, and some of my earlier tires are really greasy, for lack of a better word... The rubber is, maybe, "sweating" something out with age? I dunno. 

I read an earlier post, from 2014 or so, about tire storage, and it was helpful, but not as specific an answer as I was looking for. Any thoughts, yea or nay?
I really expected someone with chemistry leanings to explain to us what was "migrating" out of the rubber with time or temperature, to make them "greasy"...much like cocoa butter will migrate outside of M&amp;M's that have gotten too hot in their package.  

The question "chicks" linked to gives some good answers though, and it's encouraging that no one has had any storage tragedies.  Still, I would advise keeping them out of the usual culprits though:  sunlight and hot temperatures.