Film base layer coming off post process - I thought base was base !?

[nick mulder]

Suspect I'm about to learn something about film probably well over due...

Efke 100 11x14" film - processed in Pyro PMK

One sheet drying I noticed some residue on the base side of the film, what I thought might have been perhaps some left over wetting agent from some other negs - some sort of contamination anyway.

I touched it, it was hard and had relief - I took the neg and bathed it in water rubbing the area lightly over time it went but upon pulling out the film I noted I had rubbed off an area of some gummy layer (the film was dry to look at, but still sticky to touch before I washed it again). Under this gummy layer was the base proper, shinier and what I would usually expect ...

What is this layer ? And how to go about not affecting it ? Its pretty much like emulsion (yes, I double checked it wasn't actual emulsion like say x-ray film), a bit thicker maybe, it comes off like goo on your finger nail if you give it a good go at ... Something to do with the Anti-Halation layer ?

Anyway, the layer had pyro stain in it so the neg is now compromised in that area, but it may still print ok if eyeballing is any guide (which it often isn't with pyro and UV processes)...

 

[Erik L]

Nick, I've had that happen once with efke 100 11x14 as well. I let it dry and then cleaned the spot with pec film cleaner. I thought it was something in my final rinse tray I didn't catch at first, but it fits your description pretty well. In my case it didn't adversely affect the negative and washed off. In other words, you are not alone, but I have no idea what the culprit is
erik

 

[Photo Engineer]

Many sheet films have a matting layer on the back for retouching. Are you sure this is not what you are seeing?

PE

 

[nick mulder]

Many sheet films have a matting layer on the back for retouching. Are you sure this is not what you are seeing?

PE

ahhh - ok, something that lets pencil and markers adhere/work in ?

Well, yeh, reckon compared to the base itself it would work that way - so it's likely right ?

Erik - problem is that this layer has soaked up some pyro stain, effectively giving the base side an extra '+F' to everything but the affected area for UV exposure...

So I must have roughed it up when it was soft, must take care with both sides of the neg then ...

 

[nick mulder]

Of interest maybe is that now I have the neg dried and in a contact print frame with a bit of pressure I can see a heap of newtons rings around the area in discussion, due no doubt to the air gap being larger with the missing material.

I wonder if the rings will cause any UV banding... only one way to find out - damn, and its the good neg too, bound to be huh ...