B&W Reversal - Film base abraded by bleached silver?

[amuderick]

I continue to refine my B&W reversal process and I have a question.

I notice the my latest films are covered in tiny pockmarks...like my windshield looked after I drove too fast through the sandy wind at the beach. The defects appear on both sides of the film. So, I am thinking that something scratched the heck out of my photo. The biggest change in my most recent development run was that I used continuous agitation (steel tank on Beseler Motor Base) for the bleach step. Would it be inconceivable for the particles of silver (which are about that size in the pour-off) to have abraded the film base and emulsion during extended agitation?

I ran two different films (Efke and Tmax) through the same process and they came out with the same pockmarks so I am sure it is not a manufacturer defect.

A sample photo is attached. It is a 100% crop of a 1200DPI scan. The marks on the emulsion side (down) appear white and those on the base side (up) appear black. When I hold the slide up to the light, they all appear white.

If not the silver particles, then what? And if so, that is not good. Ideas?

 

[railwayman3]

I don't quite follow what you say about suspended silver particles....I would have thought that the silver was dissolved out as a soluble chemical compound, not remain in the liquid as bits in metallic form?
Looking just at the picture, I'd have said that there was some kind of undissolved chemical in the solution which had settles on the film, or even dirt particles (two of the black marks look like fibres). Could anything have stuck to the films during drying?

 

[amuderick]

I noticed this on the films when they came out of the final rinse. It is possible that one or two of the marks are dirt or fibers (I did not really attempt to get a super-clean scan because the shot is ruined anyway). Most of them are definitely not. They cannot be washed off. They cannot be scratched off. You can feel them with your finger though.

When I pour out my permanganate bleach, the silver is not in solution as a salt or in suspension. It is tiny black particles, (silver sulphide maybe?), that if left for a few minutes in a bottle, will sink to the bottom.

 

[railwayman3]

If you can feel the particles stuck in the emulsion after the final rinse, it seems that (whatever they are) they must have actually attacked the emulsion chemically in some way to attach themselved during the processing.

I'm thinking that any inert dust or fibre particles in the solution would just tend to float around and probably wash off in the final rinse. And even that any particles in the solutions would not be abrasive enough to do damage just by swishing around during the agitation. Which brings me back to wondering about un-dissolved chemicals?

Noticing that you are refining your process, is there anything else in your technique or chemistry which you have changed this time?

It's a while since I studied my photographic chemistry, so would need to swot up again, but silver sulphide is certainly insoluble and brown-black in color.

Edit - Just found a reference that permanganate bleach can soften the emulsion more than others, and a mention that of an old Gevaert reversal formula using a Chrome Alum hardener to avoid this. Will read this up when I have more time (work in the morning now!).

 

[Photo Engineer]

Silver metal bleached during processing is not capable of scratching film. Neither is the fixed product. Whatever it is, it is something else.

PE

 

[PHOTOTONE]

Good clean practices in rinsing and drying reversal film should solve your issues. I think it is sediment and dirt drying on the film. After you process you should as a final rinse, Soak your film for 1 minute in a bath of Photo-flo solution (or other similar wetting-agent) made from distilled water and Photo-flo concentrate, then hang up. Then take 2 photo-sponges which have been soaking in water, wring them out, then soak them in the Photo-flo, wring out then gently squeegy the film between the 2 sponges, starting at the top, going to the bottom. Use a light touch, and only once. Then leave your film to dry in an area without air movement. It should be much better than your example. Use your Photo-flo working solution solution only once.

 

[amuderick]

Thanks for all your info. Good to know all of this. I will troubleshoot and see if I can't figure out a more mundane reason. I'll post it when I discover it.

 

[Ian Grant]

The probable cause is frilling of the emulsion on the edges of the EFKE film. They aren't fully hardened like other films and are prone to problems of softening.

Your scan looks exactly like what occurs when tiny pieces of emulsion adhere to film, these pieces are sticky so can't be washed off. You will need to thoroughly clean all your dev tanks etc, filter any solutions you might reuse.

For the EFKE films I'd add a hardener to the first developer, or pre-soak in a hardening silution. Railwayman's right some processes use Potassium Alum hardener quite early in the process cycle.

Ian

 

[amuderick]

Ian, that is an interesting theory. I rewashed in tap, then distilled, then distilled w/photo-flo. No change. I will separate the Efke from the Tmax the next time I do a run and see what happens. Will hardening before bleach maintain the hardened gelatin or will the bleach cancel it out? I really prefer the Efke 100 look to Tmax so I'd like to make this work. Any formulas for hardener you can link me to?

 

[Ian Grant]

It's not a theory it's a fact Adox/EFKE films were notorious for it, although in the last few years they are very slightly better hardened. At one time if you processed too warm, or with too great a difference between chemical stages the emulsion would just come off the support.

Personally I'd use quite a strong pre-hardener first with EFKE films before the 1st developer because of the softness of the emulsion. (there was a url link here which no longer exists)

The risks of slivers of emulsion are also to any subsequent films processed in the same tanks, & chemicals. So it's wise to be extremely cautious.

Ian

 

[Photo Engineer]

All films are sensitive to the B&W bleach used. The permanganate bleaches are notorious for softening film. That is why I usually recommend dichromate bleaches.

PE

 

[dr5chrome]

yes, what PE said.
Even if you use a permanganate bleach you shouldn't have to use a hardener and any film will soften if it is not use correctly. Experiment with your solutions. There is much experimenting to be had here. What you discover on your own can be worth much more than any advice given on this forum. BTW the marks on your film look like dirt and unfinished bleaching.

dw

 

[Photo Engineer]

Alessandro, that is because the melting point of unhardened gelatin is about 20 degrees C. You are saving your film more by the temperature than by using 1/2 strength bleach. Permanganate is a film softener (or dare I say 'unhardener'?), especially mixed with sulfuric acid.

PE

 

[Photo Engineer]

Well, to start with, T-Max is an exceptionally hard film, as it uses one of the new hardening agents. I would think it might survive temperatures up to 30 deg C or even higher. I have not tried that.

Secondly, the prehardener might help, but only if the action of the bleach is just to swell the film. If it actually ruptures bonds in the gelatin, which is possible, then a prehardener will not work. I have not studied permanganate to see which reaction it is, but there are both swell inducing chemicals and bond rupturing chemicals that both give the same subjective result, soft film.

PE

 

[Photo Engineer]

According to the literature, it is possible, but I have no information on its use in a photographic process. In any event, if the permanganate - sulfuric acid mixture hydrolyzes gelatin itself, then the genipin will not fix that type of problem.

The only answer, as I see it, is to try.

PE

 

[amuderick]

Well I ran another batch using the feedback from this forum. Thought I'd post my results:

I did a run of Tmax 400-2. I used PE's advice and integrated silver solvent into the developer. Very good choice. Highlights were cleared properly and development/clearing was much more even. There was no Efke film in this batch and I experienced none of the gelatin frills which redeposited on the negative. It seems that was the cause of the horrible spots on my previous negatives.

The slides have a subtle yellow stain which I attribute to using tap water for the bleach wash step. It seems the chlorides in tap water form silver chloride which stain the negative. I've made this mistake in the bleach step and the results were horrible...a sickly green/yellow stain. This time around, the stain was subtle, and dare I say, attractive. Kind of like a subtle warm tone without the intensity of the thiocarbamide-developed chocolate slides.

I did have a few white spots on the developed slides. I'll attribute this to my difficulty in keeping things below 64F during development. My room is 80F and the water comes out of the tap at 74F. Even with ice, it is difficult to keep the whole thing cold through the whole process. I'll try an alum pre-hardener next time and see if it makes a difference.

EI seems to be around 320 for this film using this process. I exposed for 400 and things were a tad bit dark. Personally, in a slide, I like the darkness. The brighter the light behind the slide, the better it looks.