I've been Googling it, but still not sure if:
1) baking the backing of a cheap frame (some kind of pressed board) will kill mold in it
2) freezing the backing will kill mold
This week I've had 2 tiny prints returned because of mold! I never frame until a week before delivery (their shop is air-conditioned.) I'm using ultra-cheap little frames, just for display purposes, from Walmart, and I never take them out of the plastic wrappers until I'm ready.
But this year has been Very Moldy! (And it's still raining.) And in one case the mold spread to the print itself (unusual).
I suspect the mold is actually in the frame backing, not entirely from my environment. But maybe the volcano has been emitting mold-friendly vapors; who knows.