Rehalogenating color films

Hi all,

I have a project for a friend who has 200 rolls or so of undeveloped film. It's all kinds, C41, B/W, E6, mostly from the 80s and 90s. The B/W look great, even TMAX 3200. Rather than roll the dice with C41, I've had good luck processing it all in b/w chemicals (XTOL seems particularly good), then scanning them. The photographer prefers b/w look anyway. However, according to this thread:

https://www.photrio.com/forum/threads/best-option-for-20-year-old-exposed-film.143708/

tl;dr: It should be possible to bring the colors back to life essentially by bleaching the film back down to a latent image, clearing, and then sending it through a standard C41 process.

I tried that over the weekend on some negs that had OK density (original process was XTOL n+2, which worked wonders), and it wiped the entire image off, including the film writing on the edge (minus some dark patches where film touched reel). The only step where I differed was in that I used some bleach I had leftover from another process, Foma FB-2 bleach, designed for reversal processing of Fomapan 100R. The formula is:
Potassium dichromate 5,0 g
Sulfuric acid conc. 10 ml
3 Water to make 1000 ml

I know my C41 process was good since I processed (everything Flexicolor, jobo) another 6 rolls in the same container and they came out beautifully.

source: https://www.foma.cz/en/fomapan-R-100

The films in question were Kodak Ektapress 1600, and I don't recall the other.

So, I have questions.
1. What could have caused the loss in image? Wrong bleach? Emulsion washed off? Any tips on how I can tell what went amiss? during that process, I exposed them to room light, is that too much/little?
2. Since I initially processed the film n+2 time, should I have processed them +2 stops C41? Or does the original n+2 development somehow bring out the silver?
3. Does the same go for E6? I processed 5 rolls of E6 last night and only one came out (Velvia was good. Fujichrome, Ektachrome 64, 100, etc were dead). Cinestill chemicals this time.
4. This post
https://www.photo.net/discuss/threads/developing-20-year-old-exposed-35mm-color-film.415369
suggests another process to look into is the "high contrast aerial film process called AN-6" which is a Kodak process. Search as I might, I can't find anything on this process, if I only had formulas, that would be excellent.
5. Any tips for how to control saturation and contrast in color film process? I can mix chemistry or supplement formulae.
6. I've done some b/w reversal processing in the past, and it seems to depend on a very strong/active first developer like Dektol, Ilford PQ, etc paper developers. Maybe the originally processed neg wasn't dense enough?
7. Any books or other good materials out there beyond typical Kodak manuals to learn what's really going on in these color processes to break them properly?

Thanks!

Thanks!

peoplemerge said:

So, I have questions.
1. What could have caused the loss in image?

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Well, in simple terms you kinda did a dumb thing. Now on the plus side that's the way I've learned many things, doing it the hard way. I'm of the opinion that when do things like that you learn them "better." Meaning that it's now clear that you didn't understand as well as you first thought you did, and now you're gonna have to learn the thing a little more thoroughly. Plus you probably won't forget it.

Here's kinda how the develop and bleach thing works in C-41. First, the light sensitive film uses mostly silver bromide. The bromide is from a class of chemical elements called halogens. When the silver is chemically combined with a halogen it can be called, generally, a silver halide. Other silver halides commonly used in photography are silver chloride, the main thing in modern color papers, and silver iodide.

Ok back to C-41 film. When you develop it, in any developer, the "exposed" parts are chemically changed into plain old metallic silver, which no longer holds onto the halide. So the halide, mostly bromide in the case of color film, comes loose and floats around in the developer as a bromide ion (an ion is just the thing with a charge on it, and the sort of thing bromide is tends have a minus 1 charge). Anyway, that bromide ion is of not much use to us, but not much we can do about it. Most of the silver halide dies NOT get developed, so it stays in the film.

Ok, now into the bleach. C-41 bleach IS a rehalogenating bleach, which means that it is gonna cause the metallic silver, which WAS gonna be happy just being silver by itself, to wanna connect up with another halide molecule IF there is one there. So, IF the bleach has free bromide ions floating, which C-41 bleach DOES, then the previously metallic silver will be converted back to a silver halide again. So we refer to this as a rehalogenating bleacb. Now, the normal significance of everything being a silver halide at this point, is that the fixer can now dissolve all of the silver halide out of the film. So a processed color neg film should have essentially NO silver left in it.

In this explanation I skipped an important part - when a color developer is used it not only converts the exposed silver halide to metallic silver, it also creates a colored dye image in film. (The dyes are formed by the "used up" developer molecule combining with a so-called dye coupler already in the film; each color layer has a specific type of coupler to determine whether it is cyan, magenta, or yellow.)

Finally to the part you really wanna know about - what happened to your image? Pretend that you had a normal C-41 process, not your special bleach. Ok, you had a good silver image to start with, but no dye image (cuz you didn't use the special color developer). Then you put it through a C-41 color developer, but since it was already a metallic silver image there was nothing for the color developer to do - everything there had already been developed. So nothing about your film changed in the color developer. Next you put your film in the C-41 bleach. The bleach basically converts all of the metallic silver (image) into a silver halide (which we know can be dissolved by fixer). Then you put the film into fixer, and everything does dissolve - the silver image that used to be there is now gone.

You should have NOT put the film into the fixer.

I'm gonna say that I've never redeveloped film like this, but here's what you should have done, in principle. Starting out with the initial silver image (a result of developing in a b&w developer) you should have simply used the C-41 bleach, converting the entire metallic silver image into a silver halide image. Then wash thoroughly (small amounts of bleach will damage the developer). Now is the time to redevelop in C-41 developer. The developer now encounters a silver halide which, provided you have exposed it to light, will be properly developed as a silver image plus a dye image. Continuing through the bleach and fix should completely remove all silver, leaving only the normal colored dye image.

If this seems too complicated to follow, just reread several times writing down the steps as you go. I can explain further if needed.

Ps, regarding your bleach, there is no halide in it so it can't be a rehalogenating bleach. I really have no idea what will happen if you use that to bleach the film and then redevelop in a color developer. Apparently it's worked for you as part of a plain C-41 process so perhaps it can also be redeveloped; I dunno. The key thing is that you start with a silver image, of some sort, that is capable of being "developed." The color developer must be able to chemically "reduce" the silver, which means that the developer molecule is simultaneously "oxidized," and it is this oxidized developer molecule that combines with the dye coupler to form a color dye. If I had to guess, I'd consider that it's possible that your bleach might adequately oxidize the metallic silver such that it will stay, for some time, in a form that CAN be developed. But it may be that some of the bromide ion in the developer might also recombine with some of the (presumably) oxidized silver before the developer can act on it. I would guess that as long as you develop in the light this would also develop, provided it gets enough time. But everything I'm saying are just guesses; you'll probably have to try it to be sure. I'd personally prefer to have a real C-41 bleach. Best of luck.

Thanks, @Mr Bill ! Yes, I'll need to reread your detailed post (many thanks!) and digest.

At first blush, having read

Mr Bill said:

You should have NOT put the film into the fixer.

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The head scratcher is the comment #15 from https://www.photrio.com/forum/threads/best-option-for-20-year-old-exposed-film.143708/ where @Rudeofus suggests

Rudeofus said:

... The procedure I suggested will give you this info as cheaply as it gets:

1. stand develop film in Rodinal 1:100 (search APUG for instructions)
2. stop bath
3. fix film
4. wash film
5. Take film out of film tank and inspect. If there is no visible image, then film rolls of that brand/speed are likely lost. Put them back in your priority so you don't waste time on a futile effort

If a film strips looks ok, then do the following:

1. mix a bleach from 5 g/l Potassium Hexacyanoferrate III and 10 g/l Potassium Bromide.
2. mix a clearing bath from 10 g/l Sodium Sulfite.
3. prepare a complete set of C-41 processing bathes, bring up to temperature.
   
4. put the black&white developed film back onto a film spindle and into a film tank.
5. bleach the film for 5-10 minutes
6. wash the film for 3-5 minutes
7. put film in clearing bath for about 1 minute
8. wash again for 3-5 minutes, ideally with 38°C wash water to bring the film tank up to temperature for C-41 process
9. then run through regular C-41 process

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I have already fixed some 30 films in this manner, so maybe it's too late for them, but not the 100+ or so I haven't gotten to yet. Instead, dev, bleach, dry, scan, then inspect and if it's worth it, bleach again, wash wash wash, then full C41 (c41 dev, bleach, fix, etc).
It does make me wonder what would have happened had I just used the Flexicolor Bleach III instead of the dichromate bleach.

In theory the only problem you'll run into is if the B&W developer you used wasn't similar enough to C41. You could get color crossover, but it may be fixable scanning.

peoplemerge said:

The only step where I differed was in that I used some bleach I had leftover from another process, Foma FB-2 bleach, designed for reversal processing of Fomapan 100R. The formula is:
Potassium dichromate 5,0 g
Sulfuric acid conc. 10 ml
3 Water to make 1000 ml

Click to expand...

So that didn't work as Mr. Bill explained.

What WOULD work is:
1. Bleach the B&W-developed film in a rehalogenating bleach. A simple ferricyanide/bromide bleach would do for this purpose.
2. Then run the entire thing through a regular C41 process: color developer, bleach, fix. In this part of the process, using a non-rehal bleach such as your dichromate bleach would be OK in principle. However, the bleach in step (1) MUST be a rehalogenating bleach as you can derive from Bill's post.

peoplemerge said:

The head scratcher is the comment #15 from https://www.photrio.com/forum/threads/best-option-for-20-year-old-exposed-film.143708/ where @Rudeofus suggests...

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Hi, I don't see anything amiss with Rudeofus' post. He gives the procedure in two parts. First is a standard sort of b&w procedure, including fixing, like you are starting out with.

His second part, steps 1-9, is the color processing part. Note that his step 7 is to use a "clearing bath," which is NOT a fixer. It presumably just improves the washing, but I would guess that a good long wash would do just as well. But again, I haven't actually done it so there may be something I'm missing. Rudeofus has been around for a while, and he tends to research things pretty thoroughly, so if he thinks this step is NECESSARY then it probably is. But again, I think it's probably just to speed up the washing (if there is any residual bleach in the film when you repeat the C-41 process it will damage the developer).

As a note, I initially presumed that in your first bleaching step you followed this with a fixer, which was the only way I saw to completely remove the image. But now, on reviewing Rudi's procedure, it occurs to me that he was not specific that the bleached film should be exposed to light. Because if the intermediate silver halide image, the result of bleaching the metallic silver image, is not capable of being developed, then the final step, the full C-41 process, will completely remove everything. So this is another possibility as to how your film ended up blank.

Fwiw I don't quite get the point of the initial development in b&w developer, unless it is just seen as cheaper method to see if there is any image at all. Personally I would probably just run the C-41 process from the start, skipping that first b&w step. But again, maybe there is something that I'm missing about this?

Best of luck with your experiments.

If you have a C-41 chemistry package with separate bleach and fixer, the C-41 bleach will work to restore the film to a state that can be developed. It would go like this:

1. pre-wet previously B&W processed film
2. bleach in C-41 bleach (NOT BLIX!! That would remove the silver too early)
3. wash thoroughly
4. apply complete C-41 process in normal order

This should restore normal color to films previously processed in B&W chemistry (as a bonus, it will remove the filter layer that produces such high "fog" density).

Dichromate bleach, Farmer's Reducer, or blix will not work for the first bleach step here, because they remove the silver without leaving a form that can be developed.

Donald Qualls said:

If you have a C-41 chemistry package with separate bleach and fixer, the C-41 bleach will work to restore the film to a state that can be developed. It would go like this:

1. pre-wet previously B&W processed film
2. bleach in C-41 bleach (NOT BLIX!! That would remove the silver too early)
3. wash thoroughly
4. apply complete C-41 process in normal order

This should restore normal color to films previously processed in B&W chemistry (as a bonus, it will remove the filter layer that produces such high "fog" density).

Dichromate bleach, Farmer's Reducer, or blix will not work for the first bleach step here, because they remove the silver without leaving a form that can be developed.

Click to expand...

Hello esteemed Donald
Which bleaching solution is best suited for this process from your point of view,
Are you a fan of copper bleach?
Why isn't there a re-exposure step?

Donald Qualls said:

If you have a C-41 chemistry package with separate bleach and fixer, the C-41 bleach will work to restore the film to a state that can be developed. It would go like this:

1. pre-wet previously B&W processed film
2. bleach in C-41 bleach (NOT BLIX!! That would remove the silver too early)
3. wash thoroughly
4. apply complete C-41 process in normal order

This should restore normal color to films previously processed in B&W chemistry (as a bonus, it will remove the filter layer that produces such high "fog" density).

Dichromate bleach, Farmer's Reducer, or blix will not work for the first bleach step here, because they remove the silver without leaving a form that can be developed.

Click to expand...

Will the rehalogenating bleach leave exposed halide or do we still need to add light?

Engineer / Rudi
Can all of these steps be done with (E100) film - replace process (C41) and use process (E6)?

C-41 and E-6 bleaches may contain silver solvents as bleach accelerators. These work great for regular processing, but may lose shadow detail in this peculiar process.

@peoplemerge : you have to be extremely careful with the nomenclature! A bleach is not the same as a BLIX, and BLIX is not the same as a fixer. I interpret your posting as "these 30 rolls have already gone through BLIX" or "these 30 rolls have already gone through bleach and fixer", and in this case you are correct: if the film has lost all its silver, there is not much you can do. If you dev&bleach, as you wrote, you'll end up with silver halide, which may or may not be developable. This is certainly not, what you want. Look through the procedure I wrote down, make absolutely sure, that you have and use the right process liquids for each step.

nickandre said:

Will the rehalogenating bleach leave exposed halide or do we still need to add light?

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I highly recommend, that you expose the bleached image to either bright light or to a reexposure agent before you start redeveloping.

Rudeofus said:

I highly recommend, that you expose the bleached image to either bright light or to a reexposure agent before you start redeveloping.

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Can't hurt, for sure. The whole thing is going to go to completion anyways so you can probably just do it in the light the whole way.

Ah, interesting! Thanks @Mr Bill and @Rudeofus for your comments... I would be lost without you guys and these ideas.

As I mentioned in my original post, I'm using everything flexicolor, which does involve a separate bleach from fix. Yep, those colossal Flexicolor III bleach containers I thought would take a lifetime to get through, I'm on my 2nd batch. I also did alluded to clearing in my original post, which I did perform. It's good to restate any steps that are unclear to posterity: yes, the bleach, wash, clear, wash was sufficient to not contaminate the developer, as the quality of the other normal C41 rolls from that batch attest.

In Rudeofus' original post, covering the b/w dev process, he strictly mentions "3. fix film" which is precisely what I did, using Formulary TF-4, which I use for all b/w films. Should that be corrected to read simply "bleach" films? My bad for mentioning flexicolor and not using flexicolor fix at this stage (though it doesn't appear to change much).

So it seems the first issue is I certainly used the wrong bleach. The two rolls are lost, which is my mistake. I'm not 100% clear if the original dev process calls for bleaching or fixing.

Edit: so in addition to flexicolor bleach, I also have Potassium Ferricyanide and Potassium Bromide on hand. I'll definitely be mixing the bleach Rudeofus cites on my next run.

For the b&w developer step:
1: develop
(2: optional; stop)
3: fix (not blix)

Then for your color reprocessing:
1: rehal bleach (flexicolor)
2: develop
3: optional stop
4: bleach
5: fix
And then finish with wash and final rinse as desired.
Fogging (chemical or light) after the 1st color bleach step.

Ah ok! So @koraks I guess I'm in good shape with the film that's only had a bleach-free fix.

For color reprocessing, the rehal bleach can either be flexicolor, or better still, the ferricyanide/bromide which might preserve some shadow detail.

peoplemerge said:

For color reprocessing, the rehal bleach can either be flexicolor, or better still, the ferricyanide/bromide which might preserve some shadow detail.

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Let me be a bit more specific about this shadow detail issue. As PE once said: a good bleach is a weak BLIX. If you look at the composition of typical E-6 and C-41 bleaches, they are all loaded with Ammonia, and some amateur formulas use even stronger silver solvents. In shadow regions there will be very little silver, and even small silver loss will be noticeable.

Since these bleaches use bromide as counter anion for the bleached silver, the ammonium ion should not be an issue - in theory at least. Therefore I recommend, that you use the Flexicolor bleach at first, and if you see too much lost shadow detail, then do a test run with ferricyanide and bromide to see, whether it improves the result.

Rudeofus said:

Therefore I recommend, that you use the Flexicolor bleach at first, and if you see too much lost shadow detail, then do a test run with ferricyanide and bromide to see, whether it improves the result.

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I'd agree with this. Sensible, both chemically and on the "try the easy way first" basis.

mohmad khatab said:

Hello esteemed Donald
Which bleaching solution is best suited for this process from your point of view,
Are you a fan of copper bleach?
Why isn't there a re-exposure step?

Click to expand...

I've never tried copper bleach, and we don't know at this point which bleach is best for this situation.

nickandre said:

Will the rehalogenating bleach leave exposed halide or do we still need to add light?

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It's been my understanding that halide produced by bleaching is in a fogged state (and silver ferricyanide is as well), but nothing says the bleaching and color redevelopment (in fact, all of the process starting from B&W developed and fixed film) can't be carried out in the light, thus ensuring adequate fogging.

Rudeofus said:

Let me be a bit more specific about this shadow detail issue. As PE once said: a good bleach is a weak BLIX. If you look at the composition of typical E-6 and C-41 bleaches, they are all loaded with Ammonia, and some amateur formulas use even stronger silver solvents. In shadow regions there will be very little silver, and even small silver loss will be noticeable.

Since these bleaches use bromide as counter anion for the bleached silver, the ammonium ion should not be an issue - in theory at least. Therefore I recommend, that you use the Flexicolor bleach at first, and if you see too much lost shadow detail, then do a test run with ferricyanide and bromide to see, whether it improves the result.

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Well ,,
This view somehow supports my view of using copper bleach.
It is based on neither ammonia nor bromide.
I don't know why everyone is ignoring this respectable bleach.

That did it! I followed the same process as last time, only using Flexicolor bleach. Thanks everyone for your contributions!



Not half bad for a 20 year old photo. This was a pool player signing a poster at the world championship.

From the top, the steps I followed:
1. Develop film in b/w developer. I'll need to check my notes on time and temp.
2. Water stop.
3. Fix with TF4
4. Rinse, Permawash 2m, Wash 10m
5. Wet with photoflow
6. Dry overnight in film drier
7. Scan (DSLR, film held in enlarger)
8. Select rolls worth rehalogenating (probably 1 roll in 15)
9. In room light, bleach with flexicolor (all following steps at 100F)
10. Wash 2m.
11. Unroll film and to bright light
12. Clearing bath
13. Wash 5m
14. C41 dev
15. 1/4 strength stop bath 30s
16. bleach 5m
17. wash 5m
18. fix 7m
19. Wash 10m
20. Final Rinse

Looks like success to me.