bwfans said:
For common B&W films, ISO 400 or under, how long can they be kept in a dry cold place, like a freezer, and still reasonably good to use? What is the best record?
(actually I have this question for color or slide film too).
My question is caused by following interesting post and picture:
(there was a url link here which no longer exists)
ISO 25-50 Speed B&W films last a very long time. They are so slow that backround radiation is not a major factor in their decay. In adition the chemistry of these slow emulsions is very stable. There was a time that Efke didn't even put expiration dates on their PL25 sheet film. 10 years is nothing to these films. I have Panatomic X from the late 70's that is still nice.
ISO 400 and higher films are the exact opposite. They are sensitive to backround radiation and their chemistry is not as stable as slower films. Even frozen, which retards the chemical decay but not the radiation component you can see increased base fog past expiration. When this base fog becomes an issue is debatable. As Michael Smith has shown significant base fog can be dealt with and very old film used successfully.
The 100-200 speed films fall in between.
I recall reading that Sandy King had tested the base fog of Michaels film. Knowing the base fog and how old his film is would give you a feel for what to expect.
Finally there is a significant difference between a cool place like 50-60 degrees and a freezer. We have seen base fog double from what we measured in new stock just a year after expiration at cool room temperature.
