Slide glass problem

[trondsi]

I just pulled out an old box of slide mounts (Gepe Antinewton glass slides), only to find that the glass of each unused slide was covered in a foggy, slightly greasy-feeling layer. I got nervous, so I checked some slides that were actually mounted in the same way, and sure enough, there is a layer on the inside of each one. The film does not seem to be damaged. I was actually expecting the used slides to be worse than the unused ones (because the unused ones are open, and so get more air), but the unused ones are a bit worse.

What exactly is this? Fungus? These slides have never been in a particularly damp place (bookshelf), although we used to live in Montreal which is humid. Do you know a brand that does not have this problem? The last few years I have generally avoided glass altogether. Maybe that was a good choice.

 

[trondsi]

Huh, I think I managed to find something. According to the company making the slides:

"The fog comes from sodium, which is a part of the natural glass, and after some time this fog appears on the surface (it is the same phenomena that occur on the cognac glasses on the shelf at home: they get foggy after some time and needs to be washed from time to time)."

They also say that the sodium does no damage to the slides.

Except, I might add, that they look foggy until you open the glass, and wipe them.

 

[Poisson Du Jour]

For long term latent storage transparencies should ideally be removed from glass mounts. Store them in sleeves or archival card masks.