Suddenly a thin layer of residue appears on negs

[Elmarc]

I use Paterson tanks. They sit upright on the bench. Any chemistry streaks would most likely be across the film.
The only streaks along the length of my films would be from the final rinse etc. when hung up to dry vertically.

Are you using horizontal rotary tanks?

If so, that could be contributing to the stains along the length of the roll.
Remove the spiral of developed film and soak it in the final wash with the wetting agent. Placed horizontally, with the spool sitting in a bowl of wetting agent rinse.

This may be the best place to start as the reel does sit vertically throughout the whole process. Being intermittent, this may be very difficult to track down even with a strict process of elimination.

 

[Sirius Glass]

So that the water does not pool at the bottom.

Once the film is hanging, touch a paper towel to the bottom corners of the film to draw off any excess fluids.

 

[John Wiegerink]

I don't see how this can be the camera at fault. This is a (removable) residue not a light leak.

OK, I didn't read the part about being removable. Sorry!

 

[pentaxuser]

I don't see how this can be the camera at fault. This is a (removable) residue not a light leak.

Fine. I mentioned it as another member has indicated this as a possibility. As things stand you seem to be able give reasons why none of the causes that have been suggested can be right What may be helpful now is to summarise what suggestions about possible causes are wrong and why you know them to be wrong so that we can eliminate them and concentrate on those causes that are left that may still be possible causes

Otherwise you will continue receive possible causes, even those that may be unlikely and never find out what the problem is. There is a danger that once all possible causes have been mentioned even the unlikely ones, the thread will "die" and you will be no nearer an answer

It's all up to you of course in terms of how thing proceed from here


pentaxuser