View Full Version : Backside delamination of negative!

bruce terry
29-May-2006, 11:46

Using a 8x10 BPF200 neg formerly contact printed in Ziatype process numerous times I intentionally put way-to-much excess moisture in paper. (Please don't ask why).

Resulted was - no surprise - emulsion remnants on neg emulsion face (never use mylar interface, have never needed to).

Several weeks later neg was subjected to rinsing in water plus a little photoflo. Zia emulsion remnants did not come off (as a suspected they wouldn't) BUT A CLEAR LAYER ON THE ANTIHALATION BACKSIDE STARTED TO WRINKLE AND CONTRACT. Took twenty minutes to completely rub-rinse the layer off by thumb.

Neg has now dried and appears same as before (complete with the self-inflicted emulsion-side stains).

QUESTION IS WHAT WAS THIS LAYER?? Can't find anything on this type event in any reference. Any thoughts?

Donald Qualls
29-May-2006, 12:33
That's the anti-curl backing. It's gelatine, similar in composition to the subbing layer (first gelatine layer in contact with the base under the emulsion), and, as its name suggests, exists to reduce the asymmetry of forces from gelatin shrinkage during drying that causes film without anti-curl to, well, curl (develop some Efke roll film, and you'll know what I'm talking about). On sheet film, it's mostly redundant, but many sheet films still incorporate it because it provides a surface that will accept back-side pencil retouching, crocein scarlet mask, etc.

As to why it would reticulate and come off when it did -- was your water very hot, very acidic or alkaline, etc.? Normally excessive softening or shrinking of the gelatin is the cause of coatings coming off the base -- water above 100 F, for instance, will do this fairly reliably with many films, though it'll usually take off the image-side coatings as well. Could be handling while wet precipitated this, especially if it started at a corner or edge...

bruce terry
29-May-2006, 12:59
Donald - Excellent and prompt huge-light-bulb-now-above-my-head answer to my question.

FYI, water ph not excessive either way, temp out of tap about 80. RETICULATION (God, that word is so much better than delamination!!) initially showed in random spots in the center-ish area - and you may rest your case on my now dry, definitely curly neg!!!

Thanks to you I will sleep the sleep of the better-informed this nite.