I'll try and soak in water with some dish washing liquid. I hope I can salvage some good ones. Maybe for a day or two?
Gil, after two days, you may find the emulsion has already lifted from the film base. Our local climate is too warm to safely soak negatives for two days. Dishwashing liquid can accelerate that process.
Most molding and growth can not be satisfactorily removed without leaving marks. Those on the base side might be removed, but those which grew (note, past tense, since what you see now will usually be dead organisms or what's left of them, or what they left behind) will leave marks and scars.
An old negative which you are able to clean of whatever's stuck on them will be scarred- tiny lines and cracks which resulted from the organism eating through the emulsion- will be there.
Try not to wash or soak the negatives for no more than an hour. Anything you can't remove after that is probably part of the negative already or better left there because further cleaning will cause worse damage.
You're better off preserving the negatives as is, if what they contain is important, and live with the scars. The picture will be there, but slightly marred of course. Digital clean up can be a better solution.
