B&W Reversal: Dichromate Bleach with potassium bromide?

[pkr1979]

So, I have been chatting with Grok - on how two improve my B&W reversal process. And Im honestly not sure if the advise is any good or not. Anyway, Grok suggested adding potassium bromide to my bleach as it would be more similar to the dr5 process and the Geoffrey Gee dr5-clone 510-Pyro reversal process (which I have never heard of). Grok also said that switching from PQ Universal to DDX (1+4) could be an improvement and that it would not be too weak. What do you guys make of this?

 

[Donald Qualls]

I'm not the expert here, but wouldn't the presence of bromide result in some (presumably tiny) fraction of the bleached silver redepositing as silver bromide, resulting in overall fog in the final positive?

 

[pkr1979]

I have no idea. According to Grok it leads to a 'selective/surface-only bleach that penetrates only the outer layers of the emulsion and leaves silver in the deeper layers untouched for the first pass.'

 

[ChrisGalway]

Does Grok not give proper factual references for its "opinion"?

 

[pkr1979]

### My Reference for the Geoffrey Gee DR5-Clone Pyro Reversal Process

My description of the "Geoffrey Gee DR5-Clone" pyro reversal process is drawn from a synthesis of historical discussions and technical literature on pyro-based reversal processing, primarily from the early 2010s era of analog photography forums. While there isn't a single, canonical "official" publication under that exact name (as these were often informal shared formulas among enthusiasts approximating the proprietary dr5 process by David Wood), the core elements—pyro first developer, masked permanganate bleach, and high-energy redeveloper—stem from community-tested approximations discussed on APUG (now Photrio.com).

#### Primary Sources
- **Photrio.com (formerly APUG) Forum Threads (circa 2007–2012)**: The most direct references come from archived APUG threads where Geoffrey Gee (an active member) and others like Sandy King shared pyro reversal experiments. For instance:
- Discussions on pyro staining effects in reversal (e.g., Haist references for adjacency effects) tie into Gee's contributions on adapting WD-2D+ and PMK Pyro for first developers.
- Threads on "pyro reversal" and "DR5 approximations" (e.g., selective bleaches with halide masks) describe formulas matching what I outlined, including 5g pyrogallol, high sulfite (100g), and carbonate activation.
- Key example: A 2010 APUG thread on "Pyro for Reversal" details Gee's variant using permanganate + NaCl/KBr masking for surface bleaching, achieving ~70–80% of dr5's Dmax on Tri-X. (Search Photrio for "Gee pyro DR5" or "pyro reversal clone" to access archived posts.)

- **G. Haist, *Modern Photographic Processing* (Vol. 1, 1972, pp. 174–175)**: This is the foundational technical reference for pyro stain and adjacency effects in reversal, which Gee explicitly cited in forum posts. It covers pyrogallol-based developers with high sulfite for edge sharpening, directly informing the first developer formula I provided.

#### Additional Context
- These approximations emerged as hobbyists reverse-engineered dr5's "secret sauce" (selective bleach and pyro first dev) without proprietary details from David Wood's lab.
- No exact "Gee recipe PDF" exists publicly, but the formula aligns with variants like Geoffrey Gee's WD-2D+ adaptations shared on APUG/Photrio, cross-referenced with Kodak's legacy reversal guides (e.g., J-1 for phenidone-ascorbate second devs).
- Recent discussions (2023–2025) on Reddit and Photrio still reference these as "DR5 clones," confirming their ongoing use for films like Tri-X and Orto 50.

If you'd like me to pull specific thread excerpts or adapt the recipe further, let me know!

 

[flavio81]

Grok suggested

Found the problem!

You should never trust in whatever text an LLM outputs.

 

[pkr1979]

I know - thats why I asked.

 

[Raghu Kuvempunagar]

There's a Dichromate bleach that has Sodium Chloride and Acetic Acid in it (which I came to know from @Ole). It works as a rehalogenating bleach and can be used for Chromium intensification of slides and negatives. Replacing Chloride in that bleach with a Bromide might also serve the same purpose. But reversal bleach is usually Dichromate and Sulphuric Acid which is a much stronger acid than Acetic Acid. When a Bromide is added to reversal bleach, I would expect Bromine to be liberated because of the reaction between Sulphuric Acid and Bromide. There's probably nothing to gain from the addition as far as application in reversal processing is concerned.

Using a staining developer as the first developer is a bad idea. The stain formed by the he first development can't be removed by the bleach and acts as fog. However, Catechol based second developers (e.g. Pyrcocat HD) often give an attractive chocolate brown tone to the slides and are useful. It's also possible to increase DMax of slides by using a combination of Chromium Intensification and Catechol redevelopment.

 

[koraks]

I think the safe conclusion is that at this point, Grok is not yet the right way to try and optimize a niche photochemical process.
@pkr1979 keep in mind that LLM's can only base their answers on data actually present in the dataset they're trained on, and will then do non-linear extrapolations on it. This is a recipe for rather random, unreliable hallucinations. That might be OK if you're trying to find a recipe for banana bread using only the ingredients you just found in your cupboard; there's a decent number of recipes out there and the odds that an LLM will come up with something that turns out to be edible is OK. But for film reversal, I think the outlook is a little more bleak.

And no, there's no reason why you'd want a halide in a B&W reversal bleach, or why you'd use a staining developer especially as the first developer, and out of all options, 510 pyro would be just about the last I'd think of.

 

[Raghu Kuvempunagar]

there's no reason why you'd want a halide in a B&W reversal bleach,

It depends on the bleach. You would want a halide (Chloride specifically) in Copper Sulphate reversal bleach without which the bleach won't work.

 

[koraks]

Well, yeah. For a regular dichromate or permanganate bleach.

 

[pkr1979]

Thanks fellas

 

[Ian Grant]

Reversal bleaches must contain no Halides, that's Bromide, Chloride, or Iodide, because Silver Halides are insoluble. The Reversal bleach converts the developed Silver into a soluble salt which is washed out.

Bleaches for Indirect Toning are quite different and nearly always include a Halide.

Ian

 

[1957ExaktaVarexIIa]

As I learned from about 70 or 80 rolls of reversed films, permanganate bleach works well.
Sorry I would never again take the health risk to use dichromate bleach. I know persons who suffered from cancer.

 

[koraks]

I know persons who suffered from cancer.

Me too. None related to the use of dichromate, though. Do you?
This is not to advocate for the use of dichromate, but keep in mind that as long as it's handled in a reasonable sane/sensible manner, it's not an inherent health risk. Wear gloves, don't dust it all over the place, don't eat it.

 

[Donald Qualls]

as long as it's handled in a reasonable sane/sensible manner, it's not an inherent health risk. Wear gloves, don't dust it all over the place, don't eat it.

I'd rather do reversal with dichromate bleach than be around a smoker at home. Still looking for that perfect reversal bleach, though -- fast, thorough, safe, and cheap. Almost sure it doesn't exist, but only almost sure.

 

[pkr1979]

I switched to dichromat because it is easier to deal with - I do handle it with care.

 

[relistan]

@pkr1979 I'd suggest that you'll end up fogged at best by adding bromide. Using a more diluted developer is going to be worse for first developer certainly. For second it doesn't matter as much as long as it goes to completion. But you have done a lot of reversal and know what you're doing by now and I'm sure that this is what you also thought!

I tried some photochemical stuff out on several AI agents earlier this year. They were hopeless at formulas, one even suggesting a developer with something like 400g metol.

 

[pkr1979]

@pkr1979 I'd suggest that you'll end up fogged at best by adding bromide. Using a more diluted developer is going to be worse for first developer certainly. For second it doesn't matter as much as long as it goes to completion. But you have done a lot of reversal and know what you're doing by now and I'm sure that this is what you also thought!

I tried some photochemical stuff out on several AI agents earlier this year. They were hopeless at formulas, one even suggesting a developer with something like 400g metol.

I was pretty puzzled by Grok's suggestions, but I did get curious

 

[Rudeofus]

Reversal bleaches must contain no Halides, that's Bromide, Chloride, or Iodide, because Silver Halides are insoluble. The Reversal bleach converts the developed Silver into a soluble salt which is washed out.

@Athiril made a reversal bleach work with chloride: the Cu2+ by itself is too weak for a bleach, it needs a halide to shift the balance towards bleached. Chloride forms a silver salt soluble in Ammonia - unlike bromide/iodide, therefore his bleach plus clearing bath worked.

The procedure described also implies, that a reversal bleach with bromide is unlikely going to work, so I join the choir of people doubting Grok's recommendation.

 

[Alan Townsend]

You need a very strong developer, like d-19 or a paper developer like dektol or d72 with a small amount of sodium thiosufate added to get highest densities for projection. Search Youtube on this. A young guy (film photography project?) has a good video on using a ferric chloride bleach with ammonia clearing and IronOut as a chemical re-exposer and final developer.

AI is not a good source for this kind of specific information. Do NOT put KBr in the bleach since you are not toning prints. Ferric chloride is used for etching circuit boards, I believe. Good way to avoid dichromates and sulfuric acid as well as re-exposure.