Questions about B&W film reversal

dcy · 2025-08-07T01:14:56-0400

Raghu Kuvempunagar said:
Relax. Where did I say anything about you experimenting that warranted the above response?

I think you read my comment with a tone that I did not intend. It is difficult to convey tone of voice and body language through text. If you re-read what I wrote and imagine a "conversational" voice, I think (hope) that you will see that what I wrote was not an attack. In a similar way, I did not feel that you were attacking. You promoted an approach that threads closer to the (in relative terms) more established path of using sulfuric acid. I tried to make the case that deviating from sulfuric acid is not uncommon and there's a history of other people wanting to do so.

dcy · 2025-08-07T03:00:58-0400

Copper Sulfate + Citric Acid vs Ferric Chloride:

I have now tested the Copper Sulfate + Citric Acid recipe as described in post #1.

I am happy to report a success. The film is clear. Naturally, at this point I cannot say anything about what the Dmax would be in film reversal (low Dmax was reported with citric acid). However, I can say that the process with copper sulfate + citric acid felt "cleaner" ---- It did not form that rust-like precipitate that I saw with the ferric chloride process.

In the images below, the film process with ferric chloride is always on top, and the one with copper sulfite + citric acid is at the bottom. I notice a slightly different tint in the clear films.

relistan · 2025-08-07T04:10:40-0400

dcy said:
Beyond that, I think every bleach has had its share of reported failures. @relistan has had limited success with his efforts to make citric acid work.

I didn’t get to test this exhaustively. I only did an experiment it two because I had it. I am pretty certain it can be made to work. But it’s leaving some (what I think is) silver citrate in the film that is not clearing with the ammonia. I had thought it _would_ because of the solubility numbers I had found. But it seems it may need a further sulfite bath or perhaps EDTA as a companion to more aggressively isolate the silver like I used in the peroxide bleach. That later may actually interfere with the copper though. Somewhere there is a solution there with enough time experimenting. I ran out off time and interest.

Donald Qualls · 2025-08-07T09:48:49-0400

Those have different Dmin, which in the denser case would give muddy highlights in the final slide; that probably occurs because the bleach system overall isn't fully dissolving the rehalogenated silver, or some silver bromide or iodide is being formed due to something like impurities in the water.

MCB18 · 2025-08-07T10:19:30-0400

Ok, so judging from this, it seems like for some reason my ammonia just isn’t working, and I honestly have no idea why. It is a kind of old bottle, I think I bought it a year ago, but it has been in a sealed container, and still smells extremely strongly so I would think it is still good. Maybe I’ll see about picking up a fresh bottle and try again.

Donald Qualls · 2025-08-07T11:52:10-0400

You can't judge the strength of ammonium hydroxide solution by smell -- 0.5% is nearly as irritating as the 3% commonly sold in supermarkets. A pH test might tell something, though I don't know what the pH of fresh ammonia solution ought to be.

Be sure to get the "clear" ammonia -- the "cloudy" kind has soap in it as well.

dcy · 2025-08-07T14:30:46-0400

MCB18 said:
Ok, so judging from this, it seems like for some reason my ammonia just isn’t working, and I honestly have no idea why. It is a kind of old bottle, I think I bought it a year ago, but it has been in a sealed container, and still smells extremely strongly so I would think it is still good. Maybe I’ll see about picking up a fresh bottle and try again.

The one from Walmart costs only $1.98. Well worth it in my opinion.

dcy · 2025-08-07T15:07:30-0400

MCB18 said:
Maybe I’ll see about picking up a fresh bottle and try again.

This is what I use. Walmart house brand --- $1.98 for 2 qt. In my city not every Walmart has it, so I drive to the second closest Walmart to my home to grab it.

Donald Qualls · 2025-08-07T15:13:54-0400

I've used Parson's brand for photographic ammonia, costs about 40% more but I have a beef with Walmart. And I usually buy a small bottle, since I've only needed a little at a time. Even for reversal bleach, one quart is probably enough at a time. Costs a little more per quart than a bigger bottle, but what does waste cost when it loses strength in the bottle?

dcy · 2025-08-07T18:12:05-0400

Donald Qualls said:
Those have different Dmin, which in the denser case would give muddy highlights in the final slide; that probably occurs because the bleach system overall isn't fully dissolving the rehalogenated silver, or some silver bromide or iodide is being formed due to something like impurities in the water.

This gave me the idea to cut another piece of film and put it straight into the fixer. That would tell us what the theoretical ideal Dmin is. Here is the result. They are both darker than the base film --- btw, the film is Wolfen NP 100 ---. Neither bleach is fully removing the developed silver, but the ferric chloride one looks a bit clearer.

When I get a chance, I'm going to test other films and I can test a version of the bleach using sulfamic acid instead of citric acid. Sulfamic is more acidic. Unfortunately I don't have sulfuric acid at home and I don't want to buy some just for this test.

MCB18 · 2025-08-07T20:37:38-0400

dcy said:
This gave me the idea to cut another piece of film and put it straight into the fixer. That would tell us what the theoretical ideal Dmin is. Here is the result. They are both darker than the base film --- btw, the film is Wolfen NP 100 ---. Neither bleach is fully removing the developed silver, but the ferric chloride one looks a bit clearer.

When I get a chance, I'm going to test other films and I can test a version of the bleach using sulfamic acid instead of citric acid. Sulfamic is more acidic. Unfortunately I don't have sulfuric acid at home and I don't want to buy some just for this test.

View attachment 404836

Out of curiosity, what film is this? I would be using Aviphot which turns almost completely clear when fixed.

dcy · 2025-08-07T21:08:10-0400

MCB18 said:
Out of curiosity, what film is this? I would be using Aviphot which turns almost completely clear when fixed.

The film is AristaPan 100 which is a rebranded Wolfen NP100 for a quarter of the price. I have pieces of other films that I can test (from memory... Kentmere 200 and 400, Fomapan 400, and a couple other ones). But I do not have Aviphot.

Oh, and I also have the ortho litho films that I want to use for large negatives.

MCB18 · 2025-08-07T21:37:13-0400

Got any Rollie films? Most of those are Aviphot.

dcy · 2025-08-07T23:11:36-0400

MCB18 said:
Got any Rollie films? Most of those are Aviphot.

I have Rollie 80S in my camera right now. It's my only Rollei. When I finish this roll I can hold on to the film lead and test it, but that won't happen soon unfortunately.

isaac7 · 2025-08-08T00:15:16-0400

dcy said:
AFAIK the only beaches that fit that definition are the "classic" potassium dichromate or permanganate bleaches. The purpose of all the XXX-chloride bleaches is to pick something a little less harmful.

After the potassium dichromate and permanganate bleaches, the next most "regular" bleach uses sulfuric acid.

Beyond that, I think every bleach has had its share of reported failures. @relistan has had limited success with his efforts to make citric acid work.

Does no one use this?

A Better Black and White Reversal Bleach with Hydrogen Peroxide

In a previous post, I described how to develop your own black and white slides using a simple bleach based on hydrogen peroxide and vinegar. This post is about an improved bleach that has a number of advantages over that one. There are a lot of patents out there from the 1970s through the late...

imager.ie

I thought that people were having good results with it? I haven't tried doing reversal processing yet but this peroxide/EDTA/Citric acid bleach sounds like it is much nicer to deal with.

dcy · 2025-08-08T00:31:11-0400

isaac7 said:
Does no one use this?

A Better Black and White Reversal Bleach with Hydrogen Peroxide

In a previous post, I described how to develop your own black and white slides using a simple bleach based on hydrogen peroxide and vinegar. This post is about an improved bleach that has a number of advantages over that one. There are a lot of patents out there from the 1970s through the late...

imager.ie

I thought that people were having good results with it? I haven't tried doing reversal processing yet but this peroxide/EDTA/Citric acid bleach sounds like it is much nicer to deal with.

I haven't tested the hydrogen peroxide bleaches yet, but they're on my radar. The article you linked to lists many problems with other peroxide bleaches and claims to solve them with that recipe. I do not have EDTA at home but you can get it on Amazon.

What I'm wondering is what's the shelf life of these bleaches and how much you can reuse them. They would be expensive if you cannot reuse them.

MCB18 · 2025-08-08T00:39:34-0400

dcy said:
I haven't tested the hydrogen peroxide bleaches yet, but they're on my radar. The article you linked to lists many problems with other peroxide bleaches and claims to solve them with that recipe. I do not have EDTA at home but you can get it on Amazon.

What I'm wondering is what's the shelf life of these bleaches and how much you can reuse them. They would be expensive if you cannot reuse them.

You can reuse them, but the peroxide will decay pretty rapidly compared to something like ferric chloride or copper sulfate. They don’t give a shelf life but I wouldn’t trust it to last much more than 2-3 months before the peroxide looses strength.

dcy · 2025-08-08T01:11:42-0400

MCB18 said:
You can reuse them, but the peroxide will decay pretty rapidly compared to something like ferric chloride or copper sulfate. They don’t give a shelf life but I wouldn’t trust it to last much more than 2-3 months before the peroxide looses strength.

Thanks!

Yeah... I had a general sense that something based on hydrogen peroxide might not have a long shelf life.

dcy · 2025-08-08T02:44:48-0400

Alright. I did another test today:

(1) I re-did the copper sulfite + citric acid bleach, this time making sure that I use distilled water for every step except for the wash steps (all of which occur after the bleach).

(2) I made up a variant of the copper sulfite bleach where I replaced the 10 g/L of citric acid by 20g/L of sulfamic acid. I verified that this indeed lowered the pH. I have pH strips that go in steps of 0.5 and according to them, the solution with citric acid has a pH of 2.0 and one with sulfamic acid has a pH around 1.0.

As far as I can see, none of this made any difference at all to the base fog. In the image below, the film strip next to the "copper sulfate + citric acid" label is the original one, and the one on the left is the new one (1).

Conclusion: This suggests that the high base fog of the copper sulfate + acid bleach is a more or less intrinsic property of the copper chloride reaction and not something that can be improved significantly by hacking the pH of the solution. As always, these results might be film dependent. The film used in this test was AristaPan 100 which is rebranded Wolfen NP 100.

Questions about B&W film reversal

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