X-ray film---some sheets fogged, others fine. What happened?
So I've jumped on the X-ray film bandwagon, as a cheap way of shooting 8x10 and for the "why the hell not" value. I ordered a single box of 100 sheets (Kodak, green-sensitive, from Z&Z Medical).
Last week, I exposed two sheets of it and all was well. I happened to pull them from the middle of the stack; I loaded them in the dark, then realized they were safelight-safe and developed them by inspection under a safelight. Since then, the box has been sitting closed in a normally lit room.
Today, I exposed two more sheets; this time I took them from one end of the stack and loaded them under the safelight, but otherwise everything was the same. They developed to uniform black; no filmholder edges. So I took another sheet (again from one end of the stack, though I'm not sure it was the same end) and developed it without loading or exposing; it developed clear (and I confirmed afterwards that the developer was still capable of blackening film).
Those are the facts as we know them. I'm trying to figure out what happened and whether I can trust the rest of this box of film!
Some inferences and speculations follow, but any of these could be wrong.
First of all, since there are no filmholder marks, the fogging happened either before loading or after unloading. After unloading, there were no differences in handling between the good and bad sheets, so they were probably fogged by the time they went in the holders.
That *could* have been from storage in a light room, but it seems odd that there would be complete fogging of two sheets and nothing on the rest; I'd expect fog at one end of everything, since the bag inside the box opens at the end, and an uneven pattern that indicated where the light was getting in.
It shouldn't be from loading under the safelight, since the same safelight hasn't caused any problems for the last test sheet or during development.
If those inferences are right, the conclusion would be that the factory-sealed box came to me with two sheets already fogged. But that seems ridiculous; how on earth would that happen?
Any thoughts? Is this something other people have seen?