Copper Sulphate B&W Reversal Bleach

[Anon Ymous]

I just tried the copper sulfate bleach, followed by an ammonia and an ammonium chloride bath, with some Retro 80S, Delta 100 and HP5 Plus pieces of already developed film. The bleach was used at 26°C, that's what the water temperature happened to be at the moment. It was 50g/l CuSO4, 50g/l NaCl and 10g/l citric acid. It was quite fast, seemingly bleaching within a minute or so, but let the film there for 2' to be on the safe side. The 26% ammonium chloride bath was at about 21°C, because dissolving it is an endothermic reaction and in any case seems to be very slow to clear film of the silver chloride. It was slow enough to prompt me to make some weak ammonia solution. Mine is supposedly 25%, but it has likely lost quite a lot after all these years. At (supposedly) 2,5% it was rather slow, but at 5% it got reasonably fast, taking about 3' to clear film. The Ilford films I tried have a tinted base, so it's not very easy to assess how clear they are, but the Retro 80S is crystal clear and there was a rather obvious yellow tint. I'm not sure how it formed, but rebleaching and fixing didn't get rid of it. Overall, it basically worked, but I can't say I am impressed. I'll likely keep using the permanganate bleach.

 

[Raghu Kuvempunagar]

I'm not Rudy but I've used Persulphate bleach. It's not strong enough to bleach the silver image produced by first development. It leaves back some density.

Another potentially useful bleach is the one used in holographic reversals, Philip's Safe Solvent Bleach. I dabbled with it but had emulsion peel off problem. Maybe it's worth revisiting.

Here's the formula of Philips Safe Solvent Bleach (PSSB) for anyone who wants to mess with:

Ferric Sulphate or Ferric Nitrate: 30g
Potassium Persulphate: 20g
Sodium Hydrogen Sulphate: 30g
Water: 1000ml

https://books.google.co.in/books?id=W9vrCAAAQBAJ&pg=PA197&lpg=PA197&dq=pssb+bleach+holographic&

 

[Raghu Kuvempunagar]

The 26% ammonium chloride bath was at about 21°C, because dissolving it is an endothermic reaction and in any case seems to be very slow to clear film of the silver chloride.

According to the solubility data, 2.76g of Silver Chloride dissolves in 1000g solution of 26.31% Ammonium Chloride at 15C. There's no mention of how long it takes for this amount of Silver Chloride to fully dissolve. Still it's a bit surprising that the solution didn't appreciably dissolve Silver Chloride from the bleached film.

 

[Raghu Kuvempunagar]

As you can see, based on reduction potential the reaction should only take place with bromide and iodide. It will take place with cloride, if there is enough copper salt and chloride salt to tip the balance, but it will be slow at best - as you observed.

Thank you for the explanation. In this context, how do bleach accelerators work? Though I'm not aware of any accelerators for Copper Sulphate bleach, they exist for some other bleaches. Thiourea in small amounts is an accelerator for Ceric Sulphate bleach.

 

[Rudeofus]

Assuming this works at all, we'd see that as the bleach slowing down or completely failing to clear the film, so it would be easy to detect (and wouldn't do anything we couldn't live with; you'd see remaining density in the highlight and rebleach with fresh solution).

It would be kind of tricky to determine the remaining sulfite level in such a bath. However: Sigma Aldrich does not offer Copper Sulfite. Internet searches for Copper Sulfite come up almost empty. This sort of tells me, that Cu2+ and SO32- won't exist in the same liquid for very long.

 

[Rudeofus]

Thank you for the explanation. In this context, how do bleach accelerators work? Though I'm not aware of any accelerators for Copper Sulphate bleach, they exist for some other bleaches. Thiourea in small amounts is an accelerator for Ceric Sulphate bleach.

Most bleach accelerators I am aware of are either strong silver solvents, or something which forms insoluble silver salts. Their aim is not to increase the redox potential of the bleach, but to make the bleach agent interact more eagerly with the silver. It is quite difficult to find the effective ones through theoretical considerations. Many feasible ones are very peculiar compounds, which are custom made for Kodak&Fuji, but generally unavailable to home amateurs. One practical obstacle is, that effective bleach accelerators are quite easy to oxidize - which is a terrible condition for a bleach ingredient.

For powerful bleaching agents (e.g. persulfate), the issue is not its redox potential, but that persulfate does not care to apply it to silver on its own. There is a proven recipe:

Ammonium Persulfate	8.5 g
Potassium Bromide	24 g
Sodium Acetate	4.5 g
Acetic Acid (glacial)	15 ml
Hydroquinone	2.2 g
Copper Sulfate	1.87 g

pH ---> 3.7

This recipe uses quinone as catalyst to unleash the powerful redox potential of persulfate onto the silver. The copper catalyzes the reaction of the persulfate with the quinone. If you mix this, it needs to stand for a few hours until enough quinone is formed. It smells awfully, but it works.
PS: I would get Potassium Persulfate instead of Ammonium Persulfate, as the latter is said to explode by itself once in a while, at least that's what PE told me.

Another bleach accelerator, in this case for Ammonium Ferric EDTA would be Mercaptotriazole. Fototechnik Suvatlar had it listed until 2018 (and may still offer it on request). Since Ferric EDTA is a much weaker bleach, a mercapto-compound can be used as bleach accelerator. The amount of Mercaptotriazole is very critical, too little is as ineffective as too much. The best way to apply this accelerator is by putting it into the prebleach. It is used up by the bleach, and having it in the prebleach allows one to reuse the bleach effectively.

Thiourea may work well as bleach accelerator, but AFAIK it oxidizes easily, so the bleach won't last long. DTOD is difficult to obtain (Suvatlar may or may not have it), but it's almost impossible to oxidize, so it may even work with more powerful bleaches.

 

[Rudeofus]

Assuming this works at all, we'd see that as the bleach slowing down or completely failing to clear the film, so it would be easy to detect (and wouldn't do anything we couldn't live with; you'd see remaining density in the highlight and rebleach with fresh solution).

It will most likely fail, because Cu2+ needs a good counter ion to oxidize the silver. Sulfite will not suffice here. If my theory is correct, this soup will give you no bleaching, regardless of whether the sulfite is still in there,

 

[relistan]

I just tried the copper sulfate bleach, followed by an ammonia and an ammonium chloride bath, with some Retro 80S, Delta 100 and HP5 Plus pieces of already developed film. The bleach was used at 26°C, that's what the water temperature happened to be at the moment. It was 50g/l CuSO4, 50g/l NaCl and 10g/l citric acid. It was quite fast, seemingly bleaching within a minute or so, but let the film there for 2' to be on the safe side. The 26% ammonium chloride bath was at about 21°C, because dissolving it is an endothermic reaction and in any case seems to be very slow to clear film of the silver chloride. It was slow enough to prompt me to make some weak ammonia solution. Mine is supposedly 25%, but it has likely lost quite a lot after all these years. At (supposedly) 2,5% it was rather slow, but at 5% it got reasonably fast, taking about 3' to clear film. The Ilford films I tried have a tinted base, so it's not very easy to assess how clear they are, but the Retro 80S is crystal clear and there was a rather obvious yellow tint. I'm not sure how it formed, but rebleaching and fixing didn't get rid of it. Overall, it basically worked, but I can't say I am impressed. I'll likely keep using the permanganate bleach.

Hey, it's great that you tried it out, thanks for doing that and posting about it. The weaker 8.5% ammonium chloride solution I tried did very little but it sounds like that's not really a worthwhile avenue given that you tested it at 26% and it was still very slow.

Regarding the obvious yellow color that remained: did you use a sulfite clearing bath? I don't know that this works with the copper sulfate bleach because my one experiment last weekend was a bust for other reasons, but the sulfite bath was able to clear the staining from the silver citrate when used with the peroxide/EDTA/citric acid bleach.

 

[relistan]

Thank you for the explanation. In this context, how do bleach accelerators work? Though I'm not aware of any accelerators for Copper Sulphate bleach, they exist for some other bleaches. Thiourea in small amounts is an accelerator for Ceric Sulphate bleach.

In the Konica patent I spent a bunch of time testing for peroxide bleaches there are a ton of combinations with various potential accelerators. See pages 14-15 here https://patentimages.storage.googleapis.com/0a/67/9c/6e39d5821bd5d7/US4277556.pdf . I don't know how many of those are applicable with copper sulfate and some of them are not reasonable to obtain. But some might be worth looking at.

 

[Anon Ymous]

@relistan No, didn't use any clearing bath.

 

[Raghu Kuvempunagar]

Most bleach accelerators I am aware of are either strong silver solvents, or something which forms insoluble silver salts. Their aim is not to increase the redox potential of the bleach, but to make the bleach agent interact more eagerly with the silver. It is quite difficult to find the effective ones through theoretical considerations. Many feasible ones are very peculiar compounds, which are custom made for Kodak&Fuji, but generally unavailable to home amateurs. One practical obstacle is, that effective bleach accelerators are quite easy to oxidize - which is a terrible condition for a bleach ingredient.

For powerful bleaching agents (e.g. persulfate), the issue is not its redox potential, but that persulfate does not care to apply it to silver on its own. There is a proven recipe:

Ammonium Persulfate	8.5 g
Potassium Bromide	24 g
Sodium Acetate	4.5 g
Acetic Acid (glacial)	15 ml
Hydroquinone	2.2 g
Copper Sulfate	1.87 g

pH ---> 3.7

This recipe uses quinone as catalyst to unleash the powerful redox potential of persulfate onto the silver. The copper catalyzes the reaction of the persulfate with the quinone. If you mix this, it needs to stand for a few hours until enough quinone is formed. It smells awfully, but it works.
PS: I would get Potassium Persulfate instead of Ammonium Persulfate, as the latter is said to explode by itself once in a while, at least that's what PE told me.

Another bleach accelerator, in this case for Ammonium Ferric EDTA would be Mercaptotriazole. Fototechnik Suvatlar had it listed until 2018 (and may still offer it on request). Since Ferric EDTA is a much weaker bleach, a mercapto-compound can be used as bleach accelerator. The amount of Mercaptotriazole is very critical, too little is as ineffective as too much. The best way to apply this accelerator is by putting it into the prebleach. It is used up by the bleach, and having it in the prebleach allows one to reuse the bleach effectively.

Thiourea may work well as bleach accelerator, but AFAIK it oxidizes easily, so the bleach won't last long. DTOD is difficult to obtain (Suvatlar may or may not have it), but it's almost impossible to oxidize, so it may even work with more powerful bleaches.

Thanks for an insightful response.

Regarding Thiourea as the bleach accelerator, at least in the case of Ceric Sulphate bleach, it is not mixed with the bleach but rather made part of the stop bath of first developer. I've used it with Ceric Sulphate bleach and it does speed up bleaching. But Ceric Sulphate bleach doesn't have much capacity and hence the issue of degradation due to thiourea didn't arise.

 

[relistan]

Well, I took the morning to attempt some experiments. I was thinking about this last night and wondered what would happen if we used ammonium chloride in the bleach instead of sodium chloride. I tried to sort through the chemistry and as I understand it, in theory it would give you copper chloride still, but but with some ammonium hydroxide in the bleach itself. Only I was nearly out of ammonium chloride, but I dug around and I found another 250g bag of it. So I was able to run some experiments like that.

Takeaways

1. Using ammonium chloride instead of sodium chloride noticeably speeds up the bleach. Seems ready to go in about 1.5 mins @ 20C. I had several ideas about why but my main thought was that it probably is dissolving some of silver chloride right away on formation, and maybe that helps drive the reaction. Times will vary by density of course.
   
2. You don't get clear film this way, but it's starting to be a reasonably effective bleach.
3. Density looks like what I was getting from peroxide/citric acid without the EDTA. But EDTA is not likely to help with copper in solution here since I think it will preferentially bond with the copper vs the silver, right?
   
4. It appears not to be blixing too much though I suspect it is blixing somewhat
5. You can eliminate the staining
6. If you use ammonium chloride in the bleach, you don't need the citric acid at all. But you get a noticeably different density and it's a little slower. This might be a better rehal bleach than using citric acid and sodium chloride.

Setup

• Fomapan 400 developed in my two bath developer 2B-4 (from a film leader). I would guess density is about 3/4 what it would be from reversal.
  
• 100 ml of copper sulfate bleach, with the following formulation:
  • 5g copper sulfate pentahydrate
  • 3g citric acid 99.9%
  • varying amounts of ammonium chloride (3-7g)
• 20g/L sodium sulfite clearing bath (same as with the peroxide bleach)
• No separate ammonia bath

I tried several different concentrations of ammonium chloride. Up to about 70g/L it continues to make a difference to the resulting density. Above that I did not see any difference to my naked eye. The lower amount resulted in some brown/yellow staining, even with the clearing bath. By the time it's at 70g/L you don't have any staining.

This is what it looked like before redeveloping:

I was worried about how much of a blix it might be, so I developed half a snippet of Fomapan 400 in Ilford Multigrade developer (not to completion) and threw the whole thing into the bleach. I can't see any noticeable reduction in density from the undeveloped section. The image below has been bleached but nothing else.

Finally, this image shows what the result is using a bleach that was made up of 70g/L ammonium chloride and 50g/L copper sulfate and nothing else, vs adding the citric acid at 30g/L. Difference in color is because this is (I think) ADOX Silvermax 100 in my 2B-1 two bath from a different leader.

 

[Murray Kelly]

Some of us use CuCl2 bleach with C-41 processing and your contribution will help compounding and the use of acidification nudge me to acidify with a smidge of HCl. Thank you for all your hands on efforts.

 

[Raghu Kuvempunagar]

Some of us use CuCl2 bleach with C-41 processing and your contribution will help compounding and the use of acidification nudge me to acidify with a smidge of HCl.

What is the pH of your bleach? For C41 processing, pH of the bleach might need to be adjusted around 6.5 (see this). Kodak SR-29 bleach, a ferricyanide based bleach that can be used for C41 processing, has a pH of 6.5.

 

[Raghu Kuvempunagar]

what would happen if we used ammonium chloride in the bleach instead of sodium chloride.

Takeaways

1. Using ammonium chloride instead of sodium chloride noticeably speeds up the bleach. Seems ready to go in about 1.5 mins @ 20C. I had several ideas about why but my main thought was that it probably is dissolving some of silver chloride right away on formation, and maybe that helps drive the reaction.

This is a very interesting experiment, Karl! Nice results! Is it the case that Ammonium Chloride, by dissolving small amounts of Silver Chloride, is driving the bleach equilibrium towards formation of more Silver Chloride? If that's the case, can one get the same effect by using reasonably small amount of Sodium Thiosulphate (say < 1g/liter) plus Sodium Chloride? It would deplete a bit of Silver Bromide too, but if the amount used is small, it might not be a (big) concern.

 

[relistan]

Some of us use CuCl2 bleach with C-41 processing and your contribution will help compounding and the use of acidification nudge me to acidify with a smidge of HCl. Thank you for all your hands on efforts.

Thanks, Murray! I'm learning things

This is a very interesting experiment, Karl! Nice results! Is it the case that Ammonium Chloride, by dissolving small amounts of Silver Chloride, is driving the bleach equilibrium towards formation of more Silver Chloride? If that's the case, can one get the same effect by using reasonably small amount of Sodium Thiosulphate (say < 1g/liter) plus Sodium Chloride? It would deplete a bit of Silver Bromide too, but if the amount used is small, it might not be a (big) concern.

Thank you! I remember now what was making me think about this idea. It was actually @Murray Kelly in his ferric EDTA bleach on this thread: https://www.photrio.com/forum/threads/ammonium-chloride.180780/#post-2370458

I am not enough of a chemist to know if that is for sure what is happening. But something is happening and yes, that is the best idea I have. Maybe @Rudeofus has a better idea of the details of this reaction. For reversal, your idea to try 1g/L thiosulfate in the bleach seems totally reasonable to me. I suspect that it could be worth playing with the amount of sodium chloride present as well: if it's the chloride ion and not the ammonia that is making the difference, more might be better. All of these things are all mixed in there together and I am not certain about the order of preference for these bonds: Silver ion, copper ion, ammonium ion, chloride ion, sulfate ion, citric acid. What I understand is that some of these might be equilibrium reactions and the amount of one or the other substance could make a big difference in the direction of the reaction with the silver. But, I could be totally wrong

EDIT: Hmm, might the copper oxidize the thiosulfate?

 

[relistan]

Found this in Patrick Dignan's "How to Compound Simplified Color Processing Formulas" this evening

I would recommend 50% more ammonium chloride!

 

[NedL]

Well, I took the morning to attempt some experiments....

I'm not sure I understand completely. When you used ammonium chloride and citric acid, you didn't need a separate ammonia bath to remove AgCl? Do we think the silver was replaced by silver citrate instead of silver chloride, which was then removed later in the fix after 2nd development?

 

[Raghu Kuvempunagar]

When you used ammonium chloride and citric acid, you didn't need a separate ammonia bath to remove AgCl? Do we think the silver was replaced by silver citrate instead of silver chloride, which was then removed later in the fix after 2nd development?

If your hypothesis is that silver acetate is being formed due to citrified Copper Sulphate, wouldn't the following experiment test it? Use a solution of Copper Sulphate and Citric Acid, without any Chloride in it, to "bleach" the developed film leader, fix and check if the film clears. Any bleaching action by citrified Copper Sulphate should be visually apparent after the bleach step as Silver Citrate is greyish white in colour.

[Edit] BTW Silver Citrate is copiously soluble in Citric Acid (23-25g/l). This implies that Silver Citrate cannot precipitate on the film when the bleach has Citric Acid in it. Any Silver Citrate formed would be immediately dissolved by Citric Acid.

 

[relistan]

I'm not sure I understand completely. When you used ammonium chloride and citric acid, you didn't need a separate ammonia bath to remove AgCl? Do we think the silver was replaced by silver citrate instead of silver chloride, which was then removed later in the fix after 2nd development?

My experiment showed that there might be a path to not needing two baths to make it work. But negatives were not thin enough to be usable yet. They are still to a large extent silver chloride after bleaching, but far less than without the citric acid. The final image shows the effect on silver removal of the ammonium chloride by itself—pretty substantial—and then with the addition of citric acid. It's pretty noticeable. If we can find a compound to complex most of the rest of it, then the amount of ammonia from the ammonium chloride in the bleach itself may be enough to dissolve the remaining silver chloride. This is similar to the approach that @kentanghk and I took with the peroxide bleach where we used both citric acid and EDTA to remove all the silver that was oxidized. But that's a very different bleach so it may not work with this one, and as mentioned EDTA is probably not the right choice so we'd need to find something else. However it does look possible from this experiment.

A question that I thought of last night: if the ammonium chloride seems to point in a direction, then what would happen if we just put the ammonia in the first bath? Downside: probably no keeping properties for the bleach or the ammonia. Upside: maybe fast, one bath, probably no chance of silver nitride with all the chloride present.

If your hypothesis is that silver acetate is being formed due to citrified Copper Sulphate, wouldn't the following experiment test it? Use a solution of Copper Sulphate and Citric Acid, without any Chloride in it, to "bleach" the developed film leader, fix and check if the film clears. Any bleaching action by citrified Copper Sulphate should be visually apparent after the bleach step as Silver Citrate is greyish white in colour.

[Edit] BTW Silver Citrate is copiously soluble in Citric Acid (23-25g/l). This implies that Silver Citrate cannot precipitate on the film when the bleach has Citric Acid in it. Any Silver Citrate formed would be immediately dissolved by Citric Acid.

If your hypothesis is that silver acetate is being formed due to citrified Copper Sulphate, wouldn't the following experiment test it? Use a solution of Copper Sulphate and Citric Acid, without any Chloride in it, to "bleach" the developed film leader, fix and check if the film clears. Any bleaching action by citrified Copper Sulphate should be visually apparent after the bleach step as Silver Citrate is greyish white in colour.

[Edit] BTW Silver Citrate is copiously soluble in Citric Acid (23-25g/l). This implies that Silver Citrate cannot precipitate on the film when the bleach has Citric Acid in it. Any Silver Citrate formed would be immediately dissolved by Citric Acid.

Raghu, yes silver citrate is reasonably soluble in water and hugely soluble in citric acid. However, I can assure you from testing both bleaches and knowing what silver citrate looks like in the emulsion, that this is silver citrate. It's a milky white color when the film is wet. The guys who tested the 9% peroxide and citric acid paper bleach were seeing it also, as brown spots when redeveloped. You raise a good point though: *why*, given how soluble it is, do we see it forming? I think what may be happening is that the acidic bath does not allow the emulsion to swell enough to dissolve it out of the emulsion. I read at some point that it tends to form large-ish crystals.

What I did not mention is that in my experiment yesterday I made up a separate citric acid clearing bath to see if that would remove it—it didn't. However, the sulfite bath does. I did not try the metabisulfite bath that @Murray Kelly suggested, but we should try that. If that doesn't work, then that might be revealing. If it turns out that we just need the emulsion to swell a bit to remove the citrate, then it might actually be that e.g. a carbonate bath would work.

 

[Murray Kelly]

raghu-kuvempunagar I missed your question. I did not add anything to the CuSO4/NaCl and my cheap pH meter indicated a pH of about 6.
The arguments are becoming a bit circular here but I have picked up a couple of ideas despite that.
Thanks to all.

 

[Raghu Kuvempunagar]

Karl,

I wanted to try your idea of using Ammonium Chloride in Copper Sulphate bleach to speed it up. So I did an experiment today.

Films:
Arista Edu Ultra 100
Orwo UN54

Bleach Formula:
Copper Sulphate: 5g
Citric Acid: 5g
Ammonium Chloride: 10g
Water: 100ml

Note: This is not exactly the formula you proposed. I used a slight excess of Citric Acid and Ammonium Chloride to check if the bleach acts as a blix by removing Silver Chloride as soon as it as formed.

I took a small strip each of Arista Edu Ultra 100 and Orwo UN54, daylight fogged inside the room, developed for 10 minutes in my experimental reversal first developer. Then I bleached both strips for three minutes at room temperature (28C), washed and fixed. Arista strip nicely cleared but Orwo strip had some density on it. I washed the Orwo strip and bleached it for the second time, about two minutes, washed and fixed. Still the strip was not fully clear. Then I bleached it for the third time, for three minutes, washed and fixed. This time the strip was clear except for a small patch suggesting that a bleaching time of 10-12 minutes is needed for best results @28C. And at 20C, the time needed could be even higher. So, while the result with Arista Edu Ultra was encouraging, bleaching time for Orwo UN54 is on the higher side.

BTW the bleach didn't remove Silver Chloride from the film in a noticeable way. The addition of Ammonium Chloride doesn't eliminate the need for a subsequent Ammonia bath to clear Silver Chloride, at least with the amount of Ammonium Chloride used in the current formula.

Next, I bleached a (developed) leader of Arista film with the bleach, washed it and attempted to clear with 5% citric acid solution. This was to test @NedL's hypothesis that Silver Citrate was being formed instead of Silver Chloride. Even after ten minutes with frequent agitation, I didn't notice any change suggesting that Silver Citrate was not present in a substantial proportion. Or perhaps a stronger solution is needed.

I'm interested in knowing the longevity of this bleach as compared to Rudman's Copper Sulphate bleach which has a very long shelf life. I'll keep the bleach stored for a month and revisit it.

 

[Raghu Kuvempunagar]

raghu-kuvempunagar I missed your question. I did not add anything to the CuSO4/NaCl and my cheap pH meter indicated a pH of about 6.

Ok, all good then.

 

[Raghu Kuvempunagar]

A question that I thought of last night: if the ammonium chloride seems to point in a direction, then what would happen if we just put the ammonia in the first bath? Downside: probably no keeping properties for the bleach or the ammonia. Upside: maybe fast, one bath, probably no chance of silver nitride with all the chloride present.

Ammonium Hydroxide is supposed to react with Copper Sulphate and precipitate Copper Hydroxide immediately. So you might end up wasting the bleach if you add Ammonia to it.

You raise a good point though: *why*, given how soluble it is, do we see it forming? I think what may be happening is that the acidic bath does not allow the emulsion to swell enough to dissolve it out of the emulsion. I read at some point that it tends to form large-ish crystals.

Regarding acidic bath not allowing swelling of the emulsion, please take a look at this post by PE and the graphs he shared. At pH < 3.5 there is substantial emulsion swell if I read the graph correctly.

 

[relistan]

Note: This is not exactly the formula you proposed. I used a slight excess of Citric Acid and Ammonium Chloride to check if the bleach acts as a blix by removing Silver Chloride as soon as it as formed.

Thanks for running some experiments and posting! Thanks, this confirms what I did yesterday as well. I tried similar yesterday but above 70g/L saw no noticeable change with added ammonium chloride as I mentioned. Once you have about 50g/L of citric acid there is no change.

I took a small strip each of Arista Edu Ultra 100 and Orwo UN54, daylight fogged inside the room, developed for 10 minutes in my experimental reversal first developer. Then I bleached both strips for three minutes at room temperature (28C), washed and fixed. Arista strip nicely cleared but Orwo strip had some density on it. I washed the Orwo strip and bleached it for the second time, about two minutes, washed and fixed. Still the strip was not fully clear. Then I bleached it for the third time, for three minutes, washed and fixed. This time the strip was clear except for a small patch suggesting that a bleaching time of 10-12 minutes is needed for best results @28C. And at 20C, the time needed could be even higher. So, while the result with Arista Edu Ultra was encouraging, bleaching time for Orwo UN54 is on the higher side.

I have not seen such slow results with the films that I tried. @Anon Ymous also replicated my results with several films, clearing in only a couple of minutes—with the NaCl version. It may be that UN54 is the slow one and not the bleach. How long does it take you normally in the sodium chloride version?

BTW the bleach didn't remove Silver Chloride from the film in a noticeable way. The addition of Ammonium Chloride doesn't eliminate the need for a subsequent Ammonia bath to clear Silver Chloride, at least with the amount of Ammonium Chloride used in the current formula.

I definitely don't think it's enough to use without a second bath in the first attempts we made here, for sure. As I said to NedL above "My experiment showed that there might be a path to not needing two baths to make it work. But negatives were not thin enough to be usable yet. They are still to a large extent silver chloride after bleaching, but far less than without the citric acid. The final image shows the effect on silver removal of the ammonium chloride by itself—pretty substantial—and then with the addition of citric acid. It's pretty noticeable. If we can find a compound to complex most of the rest of it, then the amount of ammonia from the ammonium chloride in the bleach itself may be enough to dissolve the remaining silver chloride"

However, regarding removal of silver chloride, I had completely different results. See this image. Did you use the sulfite clearing bath for 2 minutes? It seems to make a big difference. What you may be seeing as remaining chloride is in fact citrate. I suppose there might be some silver sulfate as well?

This image below is without an ammonia bath. It is not clear enough to use. But it's a lot thinner.

This also shows that citric acid being present significantly reduces density:

Next, I bleached a (developed) leader of Arista film with the bleach, washed it and attempted to clear with 5% citric acid solution. This was to test @NedL's hypothesis that Silver Citrate was being formed instead of Silver Chloride. Even after ten minutes with frequent agitation, I didn't notice any change suggesting that Silver Citrate was not present in a substantial proportion. Or perhaps a stronger solution is needed.

I'm interested in knowing the longevity of this bleach as compared to Rudman's Copper Sulphate bleach which has a very long shelf life. I'll keep the bleach stored for a month and revisit it.

Yeah I tried the same and got the same result as you: it does not do anything to put it in the citric acid bath. I am interested in knowing the longevity as well. I suspect that the ammonia will gas out unless in a container with very little air space.

To be clear: I am not claiming to have discovered anything, or have found a silver bullet. I think I found out some interesting things that might signal that more work could possibly produce a result.