One thing I really don't like about old floppies is that for certain brands etc of 5.25" floppies (and possibly 8" floppies) the media turns to mush and will get all over the drive heads (and destroy the disk)
My experience is, the magnetic coating crumbles. Friction turns the fragments into what might be called "mush". I confirm bad experiences cited with "Wabash" branded 5.25" diskettes.
Supposedly (Based on info from Chuck Guzis/sydex, though I've never tried this myself), if you dismantle the floppy by cutting open the vinyl case and removing the "cookie" inside, and put it on a baking sheet and bake it in the oven at 300F(?) for maybe 8 hours, they can be made readable again. You may need to apply some sort of sealant to the outside of the disk after baking.
This is, to be polite, flawed advice. There may be some confusion about "baking" 1/4" audio magnetic tapes - I have no details about that process. The diskette Mylar cookie will distort with heat - period. So will the plastic envelope. Distortion temperatures are likely above, 120, 130 degrees F. I don't know the minimum. Storage above room temperature is not recommended. I won't say "try this to see" because someone will mess up their oven and blame me. If you try this, use all possible caution and do NOT leave your experiment unattended. I am not responsible for injury or damage to you, your oven, and certainly to your diskette. My previous post in this thread, has a link to a Web page on my site, which discusses recovery methods I'm aware of. Herb -- Herbert R. Johnson, New Jersey USA http://www.retrotechnology.com OR .net