Chemical damage to film back coating.

[MMfoto]

I've been experimenting with very long development times with Kodak TMZ 3200 and XTOL. I'm getting tan colored spots all over the back of the negatives that are one to three millimeters across, diffuse, and often slightly donut shaped. I'm assuming some sort of chemical damage to the ramjet(?)/antihalation coating from the prolonged development. Anyone have an idea?

BTW, these are absolutely not "spots" from processing residue, nor are they airbells from development, and they are on the BACK, not the emulsion.

Thanks!

 

[Neal]

Dear MMfoto,

The good news is that TMZ doesn't have rem jet coating (That is generally found on movie film.) and the antihalation layer is between the emulsion and the backing.

Of course I'm useless when it comes to a solution to your problem. The best I can think of is that you try using distilled water for mixing your chemicals.

Neal Wydra

 

[MMfoto]

Hi Neal,

So no rem jet and no antihalation coatings on the back. Hmm, is there any coating on the back? If not than that means that the spots are a deposit, and that means they aught to be able to be removed(!).

BTW, I only use distilled for my developer and TF-4.

I'm using the developer one-shot, and after one hour of semi-stand development the XTOL (1:2) looked spent. Could exhausted, and under-agitated, developer cause this kind cause staining or spots? As I said above this does not seem to affect the emulsion, only the non-emulsion, back side, of the film.

 

[Neal]

Hi MMfoto,

Having the deposits on the back seems odd to me, but assuming that the pink is the same as the sensitizing dye, it should be soluable in the same solutions.

I would find a strip with images that aren't keepers and see if the deposits wash off in Kodak Hypo Clearing Agent. I realize that TF-4 does not require HCA, but I have found that it helps with the pink using acid fixers and normal development. Quite a while back I remember reading an article on W2D2+ where the author advised using TF-4 fixer. He further advised a mixture similar to HCA to clear the dye.

In any case, I'm interested in hearing how you reslove this.

Good luck,

Neal Wydra

 

[MMfoto]

I'll try the HCA-will have to pick some up, but I'm confused by what you mean. Are you saying that the HCA might work to remove the spots, or the sensitizing dyes?

The "pink" dyes were removed well by the long processing and five minutes in TF-4. TF-4 removes these dyes pretty well, but it takes a little longer with some films like Tri-X and Neopan SS.

Thanks Neal.

 

[Shawn Dougherty]

I'm not sure about TMZ, but Kodak Tri-X definately has the antihalation coating on the back...

 

[MMfoto]

I just had a look at the negatives under a stereo microscope. For one I confirmed the spots are on the back by etching one off of a blank frame. Under the microscope most of the spots, being 2-3mm's themselves, have a tiny pin prick clear center spot that radiates out from the center to form a diffuse tan colored, well, spot. They do not come off--at all--with either alcohol, Pec-12, or lighter fluid.

The color of the spots looks very similar to stains a friend of mine had recently with XTOL on his Neopan 400. He had been using a rotary processor and reusing his XTOL (straight) for five or more development cycles. I figured his stains were from oxidization of the already taxed developer-his stains were predominately in the center of the frames where developer would drain from the slight curl of the film as the reel rolled out of the developer and into the air. Though his staining was in the emulsion not the back like mine.