B&W Reversal with ferricyanide bleach?

[Anon Ymous]

This nails it:

"Silver ferrocyanide is extremely insoluble in water, its solubility being intermediate to that of silver chloride and silver bromide. Thus, silver chloride dissolves in solutions of potassium ferrocyanide with precipitation of silver ferrocyanide, whereas silver bromide and iodide do not."

If any silver chloride were to be formed by the ferricyanide+chloride bleach's action on silver, then it will dissolve due to the presence of potassium ferrocyanide in the bleach and precipitate silver ferrocyanide again. In other words, no silver chloride is formed and ferricyanide+chloride is not a rehalogenating bleach.

So, this silver ferrocyanide can react with sodium sulfide and give solver sulfide. So, this supposedly rehallogenating bleach will somehow work when toning prints, right? Silver sulfide is far less soluble than silver bromide.

 

[Raghu Kuvempunagar]

this supposedly rehallogenating bleach will somehow work when toning prints, right?

That's because silver ferrocyanide formed imagewise on the emulsion by the action of the bleach is redevelopable by a regular developer though it is not very light sensitive.

In summary, there should be no significant difference in the bleaching result of a plain ferricyanide bleach (non-rehologenating) and ferricyanide+chloride bleach. Now, chloride can act as a very mild blix and remove some density in the lightest regions of the film/print. So the results might not be exactly identical but pretty close.

 

[mohmad khatab]

Copper sulphate bleach is definitely more stable than permanganate bleach and it can be reused several times. I've used copper sulphate bleach for over a month after mixing without any noticeable instability. The biggest complaint I've about copper sulphate bleach is that it is slow and takes 15-30 minutes in some cases.

To overcome the problem of slow bleaching.
- Deionized water should be used, not distilled water, because distilled water is not completely devoid of minerals and thus this disturbs the copper ion and makes its capabilities somewhat dispersive.
Anhydrous copper sulfate should be used, which is not cheap compared to ordinary copper sulfate.
Sodium chloride (de-iodized) should be used, not table salt.
You will get about 50% faster speed.

 

[Donald Qualls]

This nails it:

"Silver ferrocyanide is extremely insoluble in water, its solubility being intermediate to that of silver chloride and silver bromide. Thus, silver chloride dissolves in solutions of potassium ferrocyanide with precipitation of silver ferrocyanide, whereas silver bromide and iodide do not."

In summary, there should be no significant difference in the bleaching result of a plain ferricyanide bleach (non-rehologenating) and ferricyanide+chloride bleach. Now, chloride can act as a very mild blix and remove some density in the lightest regions of the film/print. So the results might not be exactly identical but pretty close.

Sigh. Okay, that's sufficient that I don't feel the need to even test it. Perhaps I could use an EDTA/chloride bleach (similar to C-41 bleach with sodium chloride added)? What's needed, clearly, is a bleach that produces a silver species that's more soluble than silver chloride. The answer might be on this chart.

 

[relistan]

Sigh. Okay, that's sufficient that I don't feel the need to even test it. Perhaps I could use an EDTA/chloride bleach (similar to C-41 bleach with sodium chloride added)? What's needed, clearly, is a bleach that produces a silver species that's more soluble than silver chloride. The answer might be on this chart.

To me from the work I did investigating peroxide bleaches, the most soluble that is easy(ish) to obtain seems like silver acetate. This in theory is dissolvable entirely in water and a normal development wash process, again in theory, should be able to wash it out. I had some success with that and not. @falotico suggested a possible sodium thiosulfate bath of low concentration after bleaching to facilitate dissolution. I have not yet tried.

I am not enough of a chemist to know what you'd need to get silver acetate from a bleach. I was attempting sodium percarbonate and vinegar as an approach.

 

[Donald Qualls]

@relistan Seemingly the only way to obtain silver acetate from image silver is with peracetic acid, which (based on recent reports in that thread) is inconsistent, tends to redeposit developable silver compounds that produce an effect similar to dichroic fog (the yellow stain), and due to gas evolution may be prone to damage soft emulsions. I was actually looking at silver salicylate on the solubility chart, and wondering if aspirin (cheap, safe to handle, low toxicity) acidified with acetic acid and doped with sodium chloride might have the desired effect -- or the aspirin/acetic solution act as a bleach independently, dispensing with the need for chloride.

I've got a long weekend starting tomorrow, I'll try to make up a test batch of salycilate bleach...

 

[relistan]

@relistan Seemingly the only way to obtain silver acetate from image silver is with peracetic acid, which (based on recent reports in that thread) is inconsistent, tends to redeposit developable silver compounds that produce an effect similar to dichroic fog (the yellow stain), and due to gas evolution may be prone to damage soft emulsions. I was actually looking at silver salicylate on the solubility chart, and wondering if aspirin (cheap, safe to handle, low toxicity) acidified with acetic acid and doped with sodium chloride might have the desired effect -- or the aspirin/acetic solution act as a bleach independently, dispensing with the need for chloride.

I've got a long weekend starting tomorrow, I'll try to make up a test batch of salycilate bleach...

Yeah, so far I don't have a 100% repeatable solution. I was not suggesting to follow that, I was only pointing out that if there were another way to make silver acetate that would be maybe a good route.

But your idea sounds very interesting and I'd love to see the experiment results!

 

[Donald Qualls]

But your idea sounds very interesting and I'd love to see the experiment results!

I'll report back here as soon as I have something.

 

[Raghu Kuvempunagar]

@relistan wondering if aspirin (cheap, safe to handle, low toxicity) acidified with acetic acid and doped with sodium chloride might have the desired effect -- or the aspirin/acetic solution act as a bleach independently, dispensing with the need for chloride.

Without an oxidizing agent, a mix of salicylic acid, acetic acid and potassium chloride won't function as a bleach. And if you are going to use it with ferricyanide, are you sure it is safe?

 

[Donald Qualls]

Without an oxidizing agent, a mix of salicylic acid, acetic acid and potassium chloride won't function as a bleach. And if you are going to use it with ferricyanide, are you sure it is safe?

It should be easy enough raise the pH into the safe range if I were to add ferricyanide -- but that wouldn't change anything, because silver ferricyanide still has the lowest solubility of the possible compounds in this system (hence would tend to form imagewise in the emulsion rather than dissolve the silver, just as it does if you add a chloride salt to a ferricyanide bleach). Perhaps benzoyl peroxide would be a better choice -- but there you'd want to avoid strongly alkaline solutions, as either one might be a (not very efficient) developing agent. Asprin is chemically similar to p-aminophenol, after all, and benzoyl peroxide is similar to salicylic acid.

 

[General Treegan]

I use Tim Rudman's copper bleach formula, it is slow but works well! This is for one of my first tests using the copper reversal bath.

 

[Raghu Kuvempunagar]

I use Tim Rudman's copper bleach formula, it is slow but works well!

That's nice! There is a thread on using copper sulphate bleach in B&W reversal processing in case you're interested.

 

[General Treegan]

That's nice! There is a thread on using copper sulfate bleach in B&W reversal processing in case you're interested.

Thanks Raghu, that threat you mention was my starting point, but it misses some big information I think, like time, temperatures and one thing that is important is that copper bleach needs to be aged.
Looking for some information on copper reversal I end reading a lot about holography, that as I can see the copper bleach comes from there.

I post it here because I read in the firsts entries that Donald writes about copper and ferricyanide. Ferricyanide will not work with ammonia as far as I understand, but copper does and very well.


My process is as follows.
Film 16mm 3378E rate as ASA25. Camera runs at 16fps, f5.6 lens 20mm.
1- pre-wash 2min in room temp water
2- 1st developer parodinal 1:25 [500ml] + 10g of sodium sulfite. 12min at room temp [around 26º]
3- wash
4- Tim Rudman copper bleach formula [http://real-photographs.co.uk/.../copper-sulfate-bleach/] 40min at 30ºC
5- cleaning bath
6- re-exposure as always
7- Diluted ammonia bath. I use MrMusculo window cleaner that is 3% ammonia hydroxide solution for 2 hours. Diluted ammonia will dissolve AgCl. Afaik will not touch AgBr that is soluble in concentrated ammonia.
8- wash
9- second developer, same as 1st one for 4min
10- Hardener fixer.

 

[Raghu Kuvempunagar]

@general: Thanks for sharing your experience with copper sulphate bleach. Though not as widely used either dichromate or permanganate bleach, copper sulphate bleach works quite well for reversal processing of B&W film. I have used the bleach on a variety of films and have no complaints about it except its slowness. In fact, for Adox CMS 20ii, it is probably the most reliable bleach as several users have had bad results with dichromate and permanganate bleaches. I reported my process for Adox CMS 20ii with copper sulphate bleach here.

Your process looks good and I've just a couple of questions.

4- Tim Rudman copper bleach formula [http://real-photographs.co.uk/.../copper-sulfate-bleach/] 40min at 30ºC

Did you use the full-strength bleach or the 1+9 diluted bleach that Rudman used for bleaching prints?

7- Diluted ammonia bath. I use MrMusculo window cleaner that is 3% ammonia hydroxide solution for 2 hours.

Did you mean 2 minutes? I use 2% ammonia and never had a need to bathe the bleached film for 2 hours in the ammonia solution! Usually the film clears in 2-3 minutes and on rare occasions I've went up to 5 minutes.

BTW hearty welcome to photrio and it's relatively small 'group' of reversal enthusiasts! I didn't notice that your first post in this thread was in fact your first post on photrio.

 

[General Treegan]

@Raghu Kuvempunagar Thanks for the warm welcome, I've been reading posts here for a long time, never post till now

I will take a look at your Adox experience, I never use adox film.

About Tim Rudman bleach I use full strength, I make a test at 20min and 30min and the results are not good and at 40min works well.
Ammonia... I say 2 hours yes! I use the window cleaner that it says is 3% and also make testes at 15,30, 60 min and results are not optimal so I leave for 2 hours and the results are as expected. I still need to try an ammonium hydroxide solution, not window cleaner.

 

[Raghu Kuvempunagar]

@Raghu Kuvempunagar
Ammonia... I say 2 hours yes! I use the window cleaner that it says is 3% and also make testes at 15,30, 60 min and results are not optimal so I leave for 2 hours and the results are as expected. I still need to try an ammonium hydroxide solution, not window cleaner.

Interesting! Who knows what other ingredients are in the window cleaner and what effect they have! Reagent grade ammonia works beautifully for our purposes. 2% solution can clear silver chloride in 2-3 minutes and without causing any harm. Worth trying if it is easy to get.

 

[relistan]

I use Tim Rudman's copper bleach formula, it is slow but works well! This is for one of my first tests using the copper reversal bath.

View attachment 264252

Nice looking images ! Thanks for sharing your process too.

 

[YoIaMoNwater]

I use Tim Rudman's copper bleach formula, it is slow but works well! This is for one of my first tests using the copper reversal bath.

View attachment 264252

Looks interesting! Just curious, the yellow cast was from your backlight right?