{Moderator note: this was split off of an existing thread here: https://www.photrio.com/forum/threads/copper-sulphate-b-w-reversal-bleach.137943 The split-off point was at this post}
Bumping this thread.
I have spent the last week or so reading this thread. First, I'm going to summarize key details in one post, bot for myself and future readers. But I do have a few questions at the end.
For me film reversal is relevant in the context of cyanotype. I currently use the "interpositive" method where I enlarge a photo to RC paper, contact print that to an ortho litho sheet film to make a large negative, and contact print that to make the cyanotype
For me, film reversal would be another way to get that large negative. The ortho litho films I have are Arista Ortho Litho Film and Inkpress Regent Royal Hard Dot Film.
(1) General Workflow:
(aggregating posts #27, #38, #73, and #87)
(2) Sodium Sulfite Working Solution:
(post #247)
Water ................... 800 ml
Sodium sulfite .......... 20 g
Water to 1L
(3) Standard Bleach (Working Solution):
(post #8 and external link to Tim Rudman's "The Master Photographer’s Lith Printing Course", now out of print).
Water ...................................... 800 ml
Copper (II) (Cupric) Sulfate................ 50 g
Concentrated Sulfuric Acid (EXTREME CARE!).. 6.5 ml
Sodium Chloride (Common Salt)............... 50 g
Water to make 1 L
You can use lower concentrations of sulfuric acid and adjust the volume. For example, battery acid is 30% sulfuric acid (post #214) so 6.5 ml becomes 22 ml. Drain cleaner is also an option.
(4) Citric Acid Variant (Working Solution):
Sulfuric acid is not an active ingredient, you just need a low pH to get copper chloride to react with metallic silver (post #228). This has encouraged @relistan and others to experiment with citric acid as milder alternative, suggesting the following recipe (post #73):
Water ...................................... 800 ml
Copper (II) (Cupric) Sulfate................ 50 g
Citric Acid (99.9%)......................... 10 g
Sodium Chloride (Common Salt)................ 50 g
Water to make 1 L
However, these efforts have had limited success and so far seem to result in staining and low Dmax (post #209).
Commentary: My understanding is that the issue is that citric acid is weaker than sulfuric. If that is the case, I might experiment with sulfamic acid. It's sold as a cleaner and if you do cyanotype you might already be using it to acidify buffered papers.
(5) Ammonium Chloride Variant (Working Solution):
(post #162)
Use ammonium chloride instead of sodium chloride. The bleach still has copper chloride to react with the silver, but also contains ammonium hydroxide. As silver chloride forms, it dissolves into the bleach itself and does not need a separate ammonia bath (post #162). But you still need the sodium sulfite bath. Best results were obtained with this formula:
Water ...................................... 800 ml
Copper (II) (Cupric) Sulfate................ 50 g
Citric Acid (99.9%)......................... 30 g
Ammonium Chloride ........................... 70 g
Water to make 1 L
Citric acid can be omitted, but with worse performance (slower bleach, more base fog).
Performance is film-dependent (post #172) and there's a risk that the ammonia hydroxide may react with sodium sulfite to make copper hydroxide (post #174), killing the active ingredient.
(6) External Variant / Ferric Chloride (Working Solution):
This variant has not been discussed here yet, but is totally based on the same principles. I found it on this YT video by Analog Resurgence (skip to 14:15).
The bleach is pure ferric chloride diluted 1+1. That is all. The mechanism is the same: Convert metallic silver into AgCl and dissolve it in ammonia. The video switches the order of the ammonia and clearing baths and the clearing bath is sodium metabisulfite instead of sulfite.
---- Q: Any idea why you'd replace sodium sulfite with metabisulfite?
Ferric chloride is used in electronic stores as a copper etchant (e.g. to make PCBs) and it is also available on Amazon.
(7) Making Adjustments:
The key variables are the initial exposure of the film and the 1st development time. In post #255, @Donald Qualls says:
"Either underexposure or underdevelopment in the first dev will result in dark final slides. If the slide is dark and there's not much separation between lights and darks, it's prob underdeveloped; if the separation is good, but everything is too dark, it's likely underexposed. If you can't be sure which, it's probably both, so start with increasing first development, then adjust exposure"
Another option to lighten the final positive overall, especially in the highlights, is to add 1 g/L of sodium thiosulfate to the first developer (post #277).
Comments: Another option is to "flash" the film, thought that is mainly for sheet film. This article by Liam Lawless has a lot to say about using a flash exposure to control contrast in the context of enlarged negatives via "classic" film reversal with potassium dichromate or permanganate.
(1) Can someone clarify for me what the sodium sulfite bath is for?
Post #265 says that it's to remove the silver citrate. That sounds like its only needed if you use citric acid for the bleach, but that can't be the full story because sulfite is also used in the original post with sulfuric acid. Post #39 says that without sodium sulfite you risk staining. Post #87 says that skipping sodium sulfite had no detrimental effect.
The YT video I linked above says that without the clearing bath, the film will be stained and look kind of sepia. But that might be specific to ferric chloride and may not be true for copper chloride.
So... I'm confused... What exactly gets removed by the sodium sulfite clearing bath?
(2) Why do some clearing baths use sodium sulfite and others metabisulfite?
I notice that film reversal with dichromate also uses sodium sulfite, just like the copper chloride one discussed in this thread. But bleach with potassium permanganate is cleared with sodium metabisulfite, as is the one with ferric chloride above.
(3) Does anyone know if any of my ortho litho films (Arista Ortho Litho vs Inkpress Regent Royal) are compatible or incompatible with this reversal process?
@Quiver2 said that some "process" films used for making internegatives might have an emulsion with AgCl, which is completely incompatible with this process. I do not know if ortho films fall into that category.
(4) Why do some posts suggest a paper developer for the first developer?
For example, posts #255 and #276 suggest Dektol 2+1.
Bumping this thread.
I have spent the last week or so reading this thread. First, I'm going to summarize key details in one post, bot for myself and future readers. But I do have a few questions at the end.
My Context:
For me film reversal is relevant in the context of cyanotype. I currently use the "interpositive" method where I enlarge a photo to RC paper, contact print that to an ortho litho sheet film to make a large negative, and contact print that to make the cyanotype
For me, film reversal would be another way to get that large negative. The ortho litho films I have are Arista Ortho Litho Film and Inkpress Regent Royal Hard Dot Film.
Summary of The Reversal Process:
(1) General Workflow:
(aggregating posts #27, #38, #73, and #87)
- First developer.
- Stop bath.
- Bleach solution --- 5 min
- Sodium sulfite solution --- 2 min
- Undiluted store bought household ammonia --- 2 min
- ----- Q: Is this when I use the room lights fog the film?
- Wash.
- Develop again.
- Wash.
- Fix.
(2) Sodium Sulfite Working Solution:
(post #247)
Water ................... 800 ml
Sodium sulfite .......... 20 g
Water to 1L
(3) Standard Bleach (Working Solution):
(post #8 and external link to Tim Rudman's "The Master Photographer’s Lith Printing Course", now out of print).
Water ...................................... 800 ml
Copper (II) (Cupric) Sulfate................ 50 g
Concentrated Sulfuric Acid (EXTREME CARE!).. 6.5 ml
Sodium Chloride (Common Salt)............... 50 g
Water to make 1 L
You can use lower concentrations of sulfuric acid and adjust the volume. For example, battery acid is 30% sulfuric acid (post #214) so 6.5 ml becomes 22 ml. Drain cleaner is also an option.
(4) Citric Acid Variant (Working Solution):
Sulfuric acid is not an active ingredient, you just need a low pH to get copper chloride to react with metallic silver (post #228). This has encouraged @relistan and others to experiment with citric acid as milder alternative, suggesting the following recipe (post #73):
Water ...................................... 800 ml
Copper (II) (Cupric) Sulfate................ 50 g
Citric Acid (99.9%)......................... 10 g
Sodium Chloride (Common Salt)................ 50 g
Water to make 1 L
However, these efforts have had limited success and so far seem to result in staining and low Dmax (post #209).
Commentary: My understanding is that the issue is that citric acid is weaker than sulfuric. If that is the case, I might experiment with sulfamic acid. It's sold as a cleaner and if you do cyanotype you might already be using it to acidify buffered papers.
(5) Ammonium Chloride Variant (Working Solution):
(post #162)
Use ammonium chloride instead of sodium chloride. The bleach still has copper chloride to react with the silver, but also contains ammonium hydroxide. As silver chloride forms, it dissolves into the bleach itself and does not need a separate ammonia bath (post #162). But you still need the sodium sulfite bath. Best results were obtained with this formula:
Water ...................................... 800 ml
Copper (II) (Cupric) Sulfate................ 50 g
Citric Acid (99.9%)......................... 30 g
Ammonium Chloride ........................... 70 g
Water to make 1 L
Citric acid can be omitted, but with worse performance (slower bleach, more base fog).
Performance is film-dependent (post #172) and there's a risk that the ammonia hydroxide may react with sodium sulfite to make copper hydroxide (post #174), killing the active ingredient.
(6) External Variant / Ferric Chloride (Working Solution):
This variant has not been discussed here yet, but is totally based on the same principles. I found it on this YT video by Analog Resurgence (skip to 14:15).
The bleach is pure ferric chloride diluted 1+1. That is all. The mechanism is the same: Convert metallic silver into AgCl and dissolve it in ammonia. The video switches the order of the ammonia and clearing baths and the clearing bath is sodium metabisulfite instead of sulfite.
---- Q: Any idea why you'd replace sodium sulfite with metabisulfite?
Ferric chloride is used in electronic stores as a copper etchant (e.g. to make PCBs) and it is also available on Amazon.
(7) Making Adjustments:
The key variables are the initial exposure of the film and the 1st development time. In post #255, @Donald Qualls says:
"Either underexposure or underdevelopment in the first dev will result in dark final slides. If the slide is dark and there's not much separation between lights and darks, it's prob underdeveloped; if the separation is good, but everything is too dark, it's likely underexposed. If you can't be sure which, it's probably both, so start with increasing first development, then adjust exposure"
Another option to lighten the final positive overall, especially in the highlights, is to add 1 g/L of sodium thiosulfate to the first developer (post #277).
Comments: Another option is to "flash" the film, thought that is mainly for sheet film. This article by Liam Lawless has a lot to say about using a flash exposure to control contrast in the context of enlarged negatives via "classic" film reversal with potassium dichromate or permanganate.
My Questions:
(1) Can someone clarify for me what the sodium sulfite bath is for?
Post #265 says that it's to remove the silver citrate. That sounds like its only needed if you use citric acid for the bleach, but that can't be the full story because sulfite is also used in the original post with sulfuric acid. Post #39 says that without sodium sulfite you risk staining. Post #87 says that skipping sodium sulfite had no detrimental effect.
The YT video I linked above says that without the clearing bath, the film will be stained and look kind of sepia. But that might be specific to ferric chloride and may not be true for copper chloride.
So... I'm confused... What exactly gets removed by the sodium sulfite clearing bath?
(2) Why do some clearing baths use sodium sulfite and others metabisulfite?
I notice that film reversal with dichromate also uses sodium sulfite, just like the copper chloride one discussed in this thread. But bleach with potassium permanganate is cleared with sodium metabisulfite, as is the one with ferric chloride above.
(3) Does anyone know if any of my ortho litho films (Arista Ortho Litho vs Inkpress Regent Royal) are compatible or incompatible with this reversal process?
@Quiver2 said that some "process" films used for making internegatives might have an emulsion with AgCl, which is completely incompatible with this process. I do not know if ortho films fall into that category.
(4) Why do some posts suggest a paper developer for the first developer?
For example, posts #255 and #276 suggest Dektol 2+1.
Last edited by a moderator:
