Iron bleaching for reversal B&W film, works, but how to improve

[Ausar]

(I'm not a native English speaker, so apologize for any gramma/spelling mistakes)

I'm looking for some safe way to make reversal B&W films.

Here are some bleach I found:

1. potassium dichromate + H2SO4 (Dangerous, I don't want to die or get cancer)
2. H2O2 +Citric Acid + EDTA + Sodium Bicarbonate https://www.photrio.com/forum/resources/b-w-reversal-bleach-—-hydrogen-peroxide-edta-citric-acid.448/
3. KMnO₄ + H2SO4
4. Copper bleach（but need ammonia water for second bath, and it's kind of dangerous)
5.cerous sulfate+h2so4，it's kind of expensive

I don't want to die, so I won't choose 1 and 4.
I don't have a lot of money, so I don't want to use 5.
2 and 3 sounds good, but, there are some problems:

1. both of them needs to mix when you use, the mixture can't last for long
2. the oxidation is too strong, some might damage your film


When I google Standard electrode potential, here is what I found:

Fe³⁺＋e⁻ ⇌ Fe²⁺ +0.77
Ag⁺＋e⁻ ⇌ Ag(s) +0.7996

This means, that although the electric potential of iron is slightly lower, trivalent iron can also oxidize silver as long as the concentration is high enough.

So, I do my test:

50g Fe2(SO4)3
15ml 37.4% H2SO4/99%Acetic acid
add water to 300ml

10min of bleaching

It did work.

Here are two test film:




But:
1.Some iron staining after bleaching
2. After second developing, my Film reel was covered by some grey matter(silver?)
3.There are a lot of particles on my film, it's hard to be wash out, I use my figer to wipe it out.
4.I need to drop the film to cleaning bath without cleaning under water, or Fe(OH)3 will stick on the film, and can't not removed

-----

So, Iron bleaching is a possible way, and it needs improvement.

Why do I know it can be improved?

Well, someone is selling a "NEW SAFE BLEACH", and it looks like this:



the color is exactly like my formula's!

But, it claimed that it's Acetic acid based, and it's PH value is 【0.2】! That doesn't make sense!

My bleach needs about 10min to sort of clean out the silver on the film, but the "SAFE BLEACH" I bought is only takes 5min( and it's already clean enought for me at 2 and half min!)

There is no silver particles stick on the film, and the film after bleach looks different

Mine bleach is white, with some grey.

while the one I bought is white, with some yellow(or green?)


I use the same film, and the same developing agent, cleaning bath(all from the "SAFE BLEACH" suit)

But, the one I bought seems much better.

I tested it on some films, the grelyish two in middle is the one I bought, the 1st and 4th one is mine.


Some info about this suit:

Bleaching: ph:0.2, 50ml solution is 58g
cleaning bath: ph:2.5


Anyone have any idea how to improve this bleaching method?

 

[Rudeofus]

How did your process run? Did you wash the film between bleaching and redeveloping? There are several things, which can go wrong here ...

 

[Ausar]

How did your process run? Did you wash the film between bleaching and redeveloping? There are several things, which can go wrong here ...

1. 1st dev
2. wash film by water to stop dev
3. bleach
4. cleaning bath
5. wash film by water
6. expose film under light
7. 2nd dev

the bleach I bought is just better than mine....

 

[relistan]

@Ausar I'm not quite sure what I'm looking at in those shots of the film. Is the top one your bleach after bleaching but before redevelopment?

In any case, the pH can quite drastically affect bleaching time and effectiveness. It might be worth getting the pH up around 2-4 for your bleach. I think you are saying it's 0.2? Not quite sure.

Interesting experiment!

 

[Ausar]

@Ausar I'm not quite sure what I'm looking at in those shots of the film. Is the top one your bleach after bleaching but before redevelopment?

In any case, the pH can quite drastically affect bleaching time and effectiveness. It might be worth getting the pH up around 2-4 for your bleach. I think you are saying it's 0.2? Not quite sure.

Interesting experiment!

First, the PH value of the bleach I bought is 0.2---ZERO POINT TWO! That is crazy! I tried adding 20g Fe2(SO4)3 and add pure Acetic acid to 50ml, then I add water to 100ml, I only got about 0.8. I don't know what did he do to get 0.2.

Also, there is an interesting thing: the bleach came as a concentrated solution in about 270ml, and add water to 500ml for use. But other concentrated solution, like developing agent, cleaning bath, are all 36ml to 500ml, so I guess the bleach is REALLY high concentration?

About the photos, the first two (next to "Here are two test film:") are after bleaching but before redevelopment, yes. I did some test with some film leaders. The 1st photo is a film leader that I submerse half into developing agent, then put into the bleach, so you might see the right half is clean(been bleached) while the left remain the original film emulsion。 The 2nd photo is a film leader that fully developed and bleached, but before cleaning bath and redevelopment.

-------

I found that Fe3+ bleach is less harmful to the film, I bleach for 15 minutes, and the film looks totally fine.When I use KMnO4, however, 5min will break my film.....

All I want to improve now are:
1. the bleach speed
2. the cleaning bath(to remove the iron from the film)

 

[1957ExaktaVarexIIa]

I do not want to disturb - but I wonder why KMnO4 bleaching has broken (damaged?) your film.

I myself have found a receipt that has worked well during almost all of my attempts with Fomapan R100, Agfapan APX100 (old!) and Rollei Infrared 400.

It contains two important things: Distilled water (instead of tap water) and additional Photo-Calgon, according to an old Agfa patent.

For 1 l bleach bath I would need:

• Liquid A: 425 ml distilled water and 75 ml H2SO4 15% and 10g Photo-Calgon
• Liquid B: 500 ml distilled water and 1,7 g KMnO4

I use to set up 220ml bleach bath for a small Jobo 510 tank which contains one 135 film.

Bleaching time: maximum 5 to 7 minutes. I am going to check out shorter times.
Yield: 3 films. I process them in one day so that the bleach bath is not left overnight.

The practical thing is that I can check the effect of the bleach bath and bleach for extra time if necessary:

• After bleaching, I open the tank and check to see if the film is lemon yellow.
• If it is lemon yellow, everything is fine.
• If it still has dark brown spots, I bleach for another two or three minutes and check again to see if it is lemon yellow. Normally, this is enough.

If necessary, I'd set up a new bleach bath and bleach on until the film is lemon yellow.

This way I have been able to bleach all 40 films I have developed so far since summer last year without any problems (after one breakdown at the beginning).

 

[Ausar]

I do not want to disturb - but I wonder why KMnO4 bleaching has broken (damaged?) your film.

I myself have found a receipt that has worked well during almost all of my attempts with Fomapan R100, Agfapan APX100 (old!) and Rollei Infrared 400.

It contains two important things: Distilled water (instead of tap water) and additional Photo-Calgon, according to an old Agfa patent.

For 1 l bleach bath I would need:

• Liquid A: 425 ml distilled water and 75 ml H2SO4 15% and 10g Photo-Calgon
• Liquid B: 500 ml distilled water and 1,7 g KMnO4

I use to set up 220ml bleach bath for a small Jobo 510 tank which contains one 135 film.

Bleaching time: maximum 5 to 7 minutes. I am going to check out shorter times.
Yield: 3 films. I process them in one day so that the bleach bath is not left overnight.

The practical thing is that I can check the effect of the bleach bath and bleach for extra time if necessary:

• After bleaching, I open the tank and check to see if the film is lemon yellow.
• If it is lemon yellow, everything is fine.
• If it still has dark brown spots, I bleach for another two or three minutes and check again to see if it is lemon yellow. Normally, this is enough.

If necessary, I'd set up a new bleach bath and bleach on until the film is lemon yellow.

This way I have been able to bleach all 40 films I have developed so far since summer last year without any problems (after one breakdown at the beginning).

I only tested once, it might because I bleach too much.

I forgot to wash my film after 1st dev, and bleached for 5min, then I found the KMnO4 turn from purple to clear, so I mix a new bleach and bath for another 3min...

also, might have something to do with my film? I tested it on lucky 400.

 

[1957ExaktaVarexIIa]

It's possible that Lucky 400 might not be able to stand the burdens of the reversal process with its changes of pH value. There are films that react quite sensitively. I also noticed this with the Rollei Infrared 400 - you have to handle it as carefully as a raw egg (as we call it in Germany ).

I suppose the problem in this case has been that you forgot to wash: so residues of the alkaline developer could have increased the pH value of the bleach bath. But then the bleach can no longer work correctly.

I noticed this in the case of a worn out bleach bath: After five minutes, everything on the film was still dark brown. As it was only a short test film, it was late in the evening and I was too lazy to prepare a new bleach bath , I simply added a little sulphuric acid to the bleach and then bleached the film again for a few minutes. Result: The film (Fomapan R100) was lemon yellow .

In your case, the total of 8 minutes in the bleach bath may simply have been too much for the Lucky 400...
In contrast, the Fomapan R100 seems to me to be quite robust (as a dedicated reversal film) - I also found a tip on the Internet to add an additional 2 minute hardening bath with potassium alum after the bleaching bath. In my experience, this seems to work well.

 

[koraks]

I forgot to wash my film after 1st dev, and bleached for 5min, then I found the KMnO4 turn from purple to clear

I suppose the problem in this case has been that you forgot to wash: so residues of the alkaline developer could have increased the pH value of the bleach bath.

Virtually anything will destroy the permanganate ion; given a suitable agent (which a photographic developer certainly has in the form of sulfite), this will happen at any pH. What it breaks down into does depend on pH, but regardless, it'll be something other than the permanganate that works as a silver bleach. Very simply put, the manganese ion in permanganate is so short of electrons (Mn7+ after all!), it'll steal them off of pretty much anything it bumps into - which can be sulfite or bisulfite, or, lacking such willing/easy victims, something more challenging like silver. This is why the wash is so important; you could consider silver being pretty far back in line for being oxidized by permanganate, so you need to get rid of easier targets first by washing them away.

One of the problems with permanganate is that it's so reactive that it will autocatalytically destroy itself in solution. As a result, solutions of permanganate are inherently unstable and don't last very well. pH affects the speed at which this happens, which is why a pH-neutral solution of permanganate keeps reasonably well, but an acidified permanganate bleach goes south really easily. So the permanganate solution I keep around for clearing the DAS stain from carbon transfers is for that reason pH neutral, and not acidified as the carbon transfer literature erroneously suggests (in fact, it doesn't need to be acidified for that purpose to begin with, neither does it require a halide in the form of NaCl.)

It's possible that Lucky 400 might not be able to stand the burdens of the reversal process with its changes of pH value.

The problem with permanganate bleaches is that they have a tendency to soften gelatin. With e.g. Foma films, this affects the subbing layer that binds the emulsion to the substrate, causing the emulsion to lift off. On films with a very soft emulsion, it may also affect the emulsion itself. Subbing is a bit of an art (after all, it's about binding a watery gel to a hydrophobic substrate) and companies like Fuji have invested quite a bit of R&D in getting it right. Where Lucky is on this spectrum, IDK but it wouldn't surprise me if the subbing technology they use is more rudimentary, like Foma's, making their films more likely to be damaged by a permanganate bleach.

 

[1957ExaktaVarexIIa]

This is interesting . Thank you!

 

[koraks]

1. potassium dichromate + H2SO4 (Dangerous, I don't want to die or get cancer)

While I applaud and support the elimination of dichromate from a process, I think it's important to note that it's perfectly easy to safely handle dichromate in a photographic application. Just don't get it into your system, and before discarding it (responsibly), reduce the CrVI into CrIII using e.g. bisulfite or ascorbic acid.

Conversely, permanganate has its drawbacks, too; it's of course a powerful oxidizing agent and will basically burn your mucous membranes if it finds its way onto them. It's also highly toxic to internal organs, extremely harmful to aquatic life and (like dichromate and any other powerful oxidizer) easily rendered into an explosive substance. Reduced to lower valences than those used in a photographic bleach, both manganese and chromium at the same time occur normally in the human body, but are toxic in cases of high exposure. The main difference between permanganate and dichromate is that the latter is a known carcinogen. This sole fact is responsible for the bad rep of dichromate, while people will consider a permanganate bleach at the drop of a hat, considering it a 'safe' alternative. I feel this lack of nuance is an unfortunate and false dichotomy.

 

[Ausar]

I look up some posts about the bleach I bought, one said that it also has cerous, not just Fe3+。

So, would that be helpful?I can't test in a couple days, wonder if someone can do the test

 

[koraks]

Cerium(IV) should work as a silver bleach, yes. Probably using cerium(IV)sulfate as the source material.
See e.g. here: https://patents.google.com/patent/US4563405A/en (in combination with DTPA), or even more concretely here: https://patents.google.com/patent/US4322493A/en
In the latter (Fujifilm) patent, cerium sulfate is used in an acidic solution. Several accelerators are used (cysteine being one of them) to improve performance.

It's kind of expensive; >€1/g in quantities that would make sense for a home darkroom user. It may be challenging to get hold of it.

 

[P C Headland]

I tried some B+W reversal a year or so back, following some guides from people processing 8/16mm movie film as a starting point. I really need to do some more messing around, but I got some passable results.

Here's some notes I took of what I did (rather than necessarily what you should do).


B+W Reversal

Step 1
Developer: Rodinal 1+25 - needs to be a “dense negative”. All films should be the same time (like colour neg)

Step 2
Bleach: 250ml Hydrogen Peroxide 3% + 15ml White Vinegar (should be run warm / hot, but take care not to “shock” the film with a big temperature change. Run for at least 6 minutes. Longer doesn’t hurt. Solution can be re-used, but leave space in container as it can expand.

Step 3
Expose film to light

Step 4
Re-develop, can use developer from step 1. Develop for normal time, though you can’t really over-develop at this stage.

Step 5
Fix as usual

Step 6
Rinse as usual


Rollei Retro 400s at 200

1. Develop in Rodinal 1+25 @23c for 15 minutes
2. Rinse / soak 10 minutes at 25c
3. Bleach @30c for 15 minutes
4. Re-expose 2-3 minutes
5. Re-develop in Rodinal 1+25 15 minutes
6. Rinse

Normal development time for Rollei Retro 400s is 10 minutes for Rodinal 1+25. Perhaps try shooting at box speed and doing first developer for same 15 minutes at 23c.


Fomapan 100 at 100

1. Develop in PC-TEA 1+30 @25c for 12 minutes
2. Bleach for 20 minutes @30c
3. Re-expose to light (bright bulb) 2-3 minutes
4. Re-develop PC-TEA 1+30 @25c for 12 minutes
5. Rinse

My notes says these came out looking OK.

Attached are some iPhone "scans" of the results, straight colour shots (i.e. not converted to B&W on the phone). The Foma ones have a very slight brownish tinge, the RR400s are nice and black

The stairs are from the Fomapan in PC-TEA (with a Ricoh 500G that needed some new light seals), the others from the Rollei Retro 400s in Rodinal 1+25 (Fujica STX-1N). Any bubble marks on the frames are of my own carelessness!

 

[Ausar]

Cerium(IV) should work as a silver bleach, yes. Probably using cerium(IV)sulfate as the source material.
See e.g. here: https://patents.google.com/patent/US4563405A/en (in combination with DTPA), or even more concretely here: https://patents.google.com/patent/US4322493A/en
In the latter (Fujifilm) patent, cerium sulfate is used in an acidic solution. Several accelerators are used (cysteine being one of them) to improve performance.

It's kind of expensive; >€1/g in quantities that would make sense for a home darkroom user. It may be challenging to get hold of it.

I know that Cerium(IV) can work as bleach, as in this article https://unblinkingeye.com/Articles/NDICRB/ndicrb.html
but, what I don't understand is, why do we need Fe3+?

 

[koraks]

what I don't understand is, why do we need Fe3+?

We don't.

I linked to two patents, and they're quite different in how they propose to use cerium.

The Konica-Minolta patent uses DTPA as the bleach, but notes that this involves problems with yellow staining of the film. They propose to use cerium (or another lanthanide) to promote oxidation of Fe(II) back into Fe(III) so that very little/no Fe(II) is available to stain the film. I suppose cerium (or another lanthanide) is present in its capacity as a catalyst here, and the concentration might be quite low. The cerium as such is not there to act as a silver bleach, per se.

The Fujifilm patent does use cerium (and only cerium) to bleach the film, but notes that there are some limitations/drawbacks w.r.t. its efficacy and levels of fog. The patent I linked to explores in particular the bleach accelerator that make the cerium bleach faster and cleaner. Unfortunately, the crucial bits of the patent (i.e. the key of which compound is used for which accelerant test) is missing from the patent text, rendering it impossible to determine which compound made for the best accelerator. This may or may not have been cysteine.

Coming back to your original comment:

the bleach I bought, one said that it also has cerous, not just Fe3+。

I suspect that your bleach may have a trace amount of cerium(IV) to prevent staining that would otherwise occur due to the formation of Fe2+ as Fe3+ steals an electron from Ag to form Ag+. Mind you, I don't know the makeup of the bleach you've got there, so I don't know for sure. The amount of cerium present would be a good indicator of what it's there for.

 

[Ausar]

We don't.

I linked to two patents, and they're quite different in how they propose to use cerium.

The Konica-Minolta patent uses DTPA as the bleach, but notes that this involves problems with yellow staining of the film. They propose to use cerium (or another lanthanide) to promote oxidation of Fe(II) back into Fe(III) so that very little/no Fe(II) is available to stain the film. I suppose cerium (or another lanthanide) is present in its capacity as a catalyst here, and the concentration might be quite low. The cerium as such is not there to act as a silver bleach, per se.

The Fujifilm patent does use cerium (and only cerium) to bleach the film, but notes that there are some limitations/drawbacks w.r.t. its efficacy and levels of fog. The patent I linked to explores in particular the bleach accelerator that make the cerium bleach faster and cleaner. Unfortunately, the crucial bits of the patent (i.e. the key of which compound is used for which accelerant test) is missing from the patent text, rendering it impossible to determine which compound made for the best accelerator. This may or may not have been cysteine.

Coming back to your original comment:


I suspect that your bleach may have a trace amount of cerium(IV) to prevent staining that would otherwise occur due to the formation of Fe2+ as Fe3+ steals an electron from Ag to form Ag+. Mind you, I don't know the makeup of the bleach you've got there, so I don't know for sure. The amount of cerium present would be a good indicator of what it's there for.

So, Fe3+ is used for making Ag to Ag+, but Fe3+ itself will be changed to Fe2+, which is bad, because it will be hard to clean(like in my experiment).
So, adding some cerium(IV) will turn the Fe2+ back to Fe3+, problem solved?

 

[koraks]

That's the gist of the Konica Minolta patent, yes. Does it work as simple as you just said? I don't know; the trick with patents is of course to accurately describe the invention so it's legally protected, but not as accurately so as to enable others to duplicate it...

 

[lamerko]

Why not try thiourea toning and rehal bleach? True, it won't have that beautiful black, but still beautiful...

 

[Ausar]

Why not try thiourea toning and rehal bleach? True, it won't have that beautiful black, but still beautiful...

what is rehal bleach? sorry I don't quite know what it is

 

[koraks]

what is rehal bleach? sorry I don't quite know what it is

"Rehal" = rehalogenating.
The idea is that you develop the negative image in the usual way. Then you fog all remaining silver halide into silver sulfide using a thiourea toner (sodium sulfide / polysulfide toner will work, too). Afterwards, you bleach the original silver negative image using a rehalogenating bleach. This can be for instance a normal ferricyanide + bromide bleach. Finally, the silver halide negative image is fixed out.

The advantage is that this can be done with quite ordinary chemistry and the process is easy and robust. The drawback is that the silver sulfide image will be brown to yellow in color. It's not possible to obtain a neutral greyscale image this way. If you like sepia toned slides, this approach works great, however.

 

[Ausar]

"Rehal" = rehalogenating.
The idea is that you develop the negative image in the usual way. Then you fog all remaining silver halide into silver sulfide using a thiourea toner (sodium sulfide / polysulfide toner will work, too). Afterwards, you bleach the original silver negative image using a rehalogenating bleach. This can be for instance a normal ferricyanide + bromide bleach. Finally, the silver halide negative image is fixed out.

The advantage is that this can be done with quite ordinary chemistry and the process is easy and robust. The drawback is that the silver sulfide image will be brown to yellow in color. It's not possible to obtain a neutral greyscale image this way. If you like sepia toned slides, this approach works great, however.

Oh, I heard of something about rehal, it's kind of easier, because AgCl、AgI or something like that is hard to dissolve, so the chemical reaction is easier to make.

But what I don't know is the toner's formula, I mean, I did hear that SnSO4 can act as a chemical reversaler, but someone said that it can't turn [all the remaining silver halide].

Can the toner you mention do the trick? Any formula I can get?

 

[koraks]

But what I don't know is the toner's formula, I mean, I did hear that SnSO4 can act as a chemical reversaler, but someone said that it can't turn [all the remaining silver halide].

You're mixing things up now, I think.
Tin(II) chloride is often used as a fogging agent, taking the place of a fogging step done with light. This simply exposes (renders developable) the silver halide in the film.
What I'm referring to is a thiourea toner, which acts on silver halide, regardless if it's exposed to light or not (it's not selective).

Can the toner you mention do the trick?

It'll convert any silver halide to silver sulfide, regardless if it's exposed or not. The process suggested by @lamerko above hence does not require a fogging step.

Any formula I can get?

Make one solution of 4% thiourea, and another solution of 4% sodium hydroxide. Add 1ml of both to 100ml of water. Use one shot. This should get the job done.
By varying the ratio thiourea to hydroxide, you can shift the tone to more yellow (less hydroxide) to brown/purple (more hydroxide).

 

[relistan]

My suggestion would be to iterate on what you are already doing @Ausar . You have something that is headed in the right direction. Try using citric acid instead of acetic acid. In all the testing I did, I found that citric acid sequestered more silver than I was able to get acetic acid to do. It will stain, however, (forms silver citrate) and requires a clearing bath like the one you are already using. Additionally, having read a lot of patents, most target pH values are like I said, in the range of 2-4 for effective bleaches. I don't think I'd want either my film or my tanks in pH 0.2 soup, never mind my extremities.

 

[Ausar]

thiourea

thiourea is hard to buy on Taobao, I don't know why. Is there any alternative formula available？