Only if they are stored under high humidity conditions.
Do you process this film yourself? If so, a processing defect is the most likely cause. Particularly reused fixer is notorious for throwing down tiny specs of dirt on the film in my experience.
These are old negatives, they haven't been recently processed or developed. I might try storing them in something else.
I don't know what the RH% is in my freezer. My 35mm slides on the other hand seem to be fine but they are stored in different materials (Print File pages).
There's no point in storing finished negative or slides in the freezer. Yes, theoretically it can make a difference in the long term, but I doubt it's overall advantageous if you take into account the risks associated with repeated freezing/thawing and condensation that are inevitable over the course of decades.
Note that museums etc. don't store negatives or slides at below-zero temperatures. They probably have good reason not to.
I've just cleaned some negatives and I have left them to hang in the bathroom at room temperature. Can anyone give me an estimate as to how long it will take for the film to dry?
I've just cleaned some negatives and I have left them to hang in the bathroom at room temperature. Can anyone give me an estimate as to how long it will take for the film to dry?