My photo boxes were waterproof but that meant they held the water the AC filled them with. I had to throw out all the prints but I have saved the negatives with seem to have grown to the sleeves. How do I try to release them, dry them and hopefully get at least some of them reprinted?
Same way the negatives were made: wash in clean water with a drop of "photo-flo" in it, hang up to dry in a cabenet to keep the dust away.
Sleeve material varies. If it made a mess, I think it is somewhat water soluable, so long time soaking will help. Eventually it woll float free, like withnused stamp collectors :) if it's archival plastic and stuck due to dried minerals or just close contact, the water with surfactant will wick in over time.
The soluability of tye minerals in water (particularly the kind that leave spots on glass, clog showers and ruin coffee pots) is sensitive to temperature. So use warm water and don't let it cool while soaking (we don't want the action to reverse). Warm, not hot, so as not to hurt the plastic.
You might want to ditch all the cheap sleeves you have, and store your negatives in archival quality sleeves (from a reputable supplier like B&H) after re-rinsing them to get out any transfer from the old plastic.