Bleaching thin negatives to redevelop in Pyro

fump · Apr 3, 2023

I have a couple rolls of film which I neglected to mark as pushed and thus severely underdeveloped--thankfully nothing terribly important. I've scanned and printed (darkroom) a couple of the best ones and they're just plain ugly. I tried a few rounds of selenium toning with modest improvement, but not enough. Then I remembered that I have a potassium ferricyanide/potassium bromide bleach (Moersch bleach concentrate) and some Nucleol and had read, in passing, about bleaching and redeveloping negatives in Pyro to build stain. Naturally I went down to the darkroom to try it out.

The theory, as I recall, is bleach until the silver is converted back to silver bromide, make sure it's been exposed to light, and then develop in Pyro until it looks good, fix, rinse and repeat.

I started at a 1:50 dilution and got no change in the negative. I repeated all the way up to 1:4 and still no bleaching action. I thought maybe Bergger Pancro was the problem so I tried an old Tri-X negative just to see and still got nothing. I was not bleaching negatives I had intensified in selenium. Am I misremembering or misconsidering? Anyone have some advice before I waste more time and bleach?

This has been a surprisingly difficult topic to research via Google, most bleaching threads are about paper which is only kind of useful here.

Andrew O'Neill · Apr 3, 2023

When I was bleaching and redeveloping a negative, I don't ever recall exposing it to light after bleaching...
Check out this thread: https://www.photrio.com/forum/threads/intensifying-a-pyro-negative.47208/

fump · Apr 3, 2023

The converted silver bromide needs to be exposed to light before redevelopment, right? Essentially recreating the latent image otherwise there's nothing to develop. It's not like a camera exposure, just bleaching in normal room light should be adequate. Maybe I'm misunderstanding.

I read through that thread, and that's the procedure I used (other than using Moersch Bleach concentrate rather than mixing my own bleach solution) and I got no bleaching or rehalogenation on either negative. I did throw them in pyro for a while just to make sure and got nothing out of the hour and a half I spent on it. That's the part that's confusing me.

grain elevator · Apr 3, 2023

fump said:
The converted silver bromide needs to be exposed to light before redevelopment, right? Essentially recreating the latent image otherwise there's nothing to develop. It's not like a camera exposure, just bleaching in normal room light should be adequate. Maybe I'm misunderstanding.

I read through that thread, and that's the procedure I used (other than using Moersch Bleach concentrate rather than mixing my own bleach solution) and I got no bleaching or rehalogenation on either negative. I did throw them in pyro for a while just to make sure and got nothing out of the hour and a half I spent on it. That's the part that's confusing me.

You got no bleaching? The image should be (at least pretty much) gone. That was not the case? Then I suppose you don't have the right bleach or right concentration.

jeffreyg · Apr 3, 2023

I know nothing about bleaching negatives but I if some are worthwhile I would first scan them. You can enlarge on to Pictorico and contact print on silver gelatin or platinum/palladium or other alt techniques. Last year I had the misfortune of having film fogged by airport X-ray and did just that. I was able to make good digital prints and pt/pd prints as well.

Sirius Glass · Apr 3, 2023

If the information is not there on the film, nothing can be done to retrieve nonexistent information.

pentaxuser · Apr 3, 2023

fump said:
The theory, as I recall, is bleach until the silver is converted back to silver bromide, make sure it's been exposed to light, and then develop in Pyro until it looks good, fix, rinse and repeat.

Can you recall where you read the theory and can you be sure what you recall reflects what was written? . I have no experience with any of this but the responses so far suggest that your recall of what you have read may not be entirely accurate

I came across a video on the subject in a place called thewebdarkroom almost immediately where the author describes what in part you seem to have done and produces an improvement His stain was not pyro but a sepia toner. However as both involve producing a stain then may be Pyro should work as well

Tim Rudman has a section on this in his toning book and claims that the above process produces the best of the intensification processes. Here's the link

Intensifying thin negatives

We try our best as film photographers to get a correct exposure every time, but occasionally there are times when we inadvertently cock it up. It may be because we have forgotten to add extra expos…

thewebdarkroom.co.uk

I hope this helps

pentaxuser

gorbas · Apr 3, 2023

You protected those negatives well with selenium toning. You should just use chromium intensifier on the first place. Now It's too late for anything else except some digital magic.

fump · Apr 3, 2023

grain elevator said:
You got no bleaching? The image should be (at least pretty much) gone. That was not the case? Then I suppose you don't have the right bleach or right concentration.

And this is what confuses me. It's a solution of 5-10% potassium bromide and 20% potassium hexacyanoferrate (ferricyanide) which works well for bleaching back fog on ancient paper. I can't figure out why it won't touch a negative.

pentaxuser said:
Can you recall where you read the theory and can you be sure what you recall reflects what was written? . I have no experience with any of this but the responses so far suggest that your recall of what you have read may not be entirely accurate

I came across a video on the subject in a place called thewebdarkroom almost immediately where the author describes what in part you seem to have done and produces an improvement His stain was not pyro but a sepia toner. However as both involve producing a stain then may be Pyro should work as well

Tim Rudman has a section on this in his toning book and claims that the above process produces the best of the intensification processes. Here's the link

Intensifying thin negatives

We try our best as film photographers to get a correct exposure every time, but occasionally there are times when we inadvertently cock it up. It may be because we have forgotten to add extra expos…

thewebdarkroom.co.uk

I hope this helps

pentaxuser

That bleach formulation is a more dilute version of the Moersch Bleach I'm using. Though even the strongest solution i tried was diluted to a weaker solution than he's using. Maybe I'll try some straight and see if that gets me anywhere.

gorbas said:
You protected those negatives well with selenium toning. You should just use chromium intensifier on the first place. Now It's too late for anything else except some digital magic.

The negatives that were selenium toned are not the same negatives I bleached. I know those are incompatible processes.

nmp · Apr 3, 2023

If nothing is happening to any one your negatives, whether or not they have been seleinum-ized, there is most likely something wrong with your bleach. What happens if you dunk a piece of developed silver gelatin paper in it?

:Niranjan.

fump · Apr 3, 2023

nmp said:
If nothing is happening to any one your negatives, whether or not they have been seleinum-ized, there is most likely something wrong with your bleach. What happens if you dunk a piece of developed silver gelatin paper in it?

:Niranjan.

Good question. I don't know why I didn't think to try, since I was standing next to a pile of test strips the whole time.

But I will.

MattKing · Apr 3, 2023

fump said:
I have a couple rolls of film which I neglected to mark as pushed and thus severely underdeveloped

There are two possible interpretations of this.
1) you gave the film ample exposure, but due to the low contrast light conditions you had planned to increase development in order to boost the contrast in the negatives, but forgot to increase development; or
2) because of low light levels or an aesthetic decision, you decided to under-expose the negatives, and then increase development in order to salvage as much as you could of the result, but forgot to increase development.
If it is the latter situation, bleach and re-develop isn't going to help you much at all. The un-exposed (due to under-exposure) silver halides were fixed away, and there is nothing in that part of the image to bleach or re-develop.
If it is the former situation, you will have something to work with. In that case, however, the forgotten extra development wouldn't have been a "push" development, it would have been an "expansion" development.
In either case, the bleached film would need exposure to light before the re-development.

Doremus Scudder · Apr 3, 2023

If you get no bleaching of an untoned negative, then your bleach is not working. That said, selenium-toned negatives may not respond well to bleaching, especially if they have been strongly toned for intensification.

I use a ferricyanide/bromide rehalogenating bleach. I use 15g potassium ferricyanide and 15g potassium bromide per liter of water, but the amounts and proportions are not that critical. The bleach should last for a fairly long time if not contaminated (e.g., with fixer, which kills bleach really quickly). I have a bottle just for bleaching negatives that's been going for a few years now.

You bleach with the lights on so you can watch the process. Bleach until the image is completely gone, except for maybe a very faint ghost of an image. The resulting silver bromide in the emulsion has been well-exposed to light since you did the whole process with the lights on. If you didn't (e.g., did everything in a tank), then, yes, you need to expose the film to light. If the film is on a reel, I'd take it off and hold it up to the light to make sure it was well and evenly exposed and then re-spool it.

Now simply redevelop in your staining developer of choice (PMK is mine) for a bit longer than your normal developing time for that film/developer combination. You can't overdevelop; you want the silver bromide to all develop to completion.

While Sirius is correct that what was not recorded on the film can't be retrieved, sometimes bleach/redevelop can give a gratifying boost to shadow detail.

Hope this helps,

Doremus

fump · Apr 3, 2023

MattKing said:
There are two possible interpretations of this.
1) you gave the film ample exposure, but due to the low contrast light conditions you had planned to increase development in order to boost the contrast in the negatives, but forgot to increase development; or
2) because of low light levels or an aesthetic decision, you decided to under-expose the negatives, and then increase development in order to salvage as much as you could of the result, but forgot to increase development.
If it is the latter situation, bleach and re-develop isn't going to help you much at all. The un-exposed (due to under-exposure) silver halides were fixed away, and there is nothing in that part of the image to bleach or re-develop.
If it is the former situation, you will have something to work with. In that case, however, the forgotten extra development wouldn't have been a "push" development, it would have been an "expansion" development.
In either case, the bleached film would need exposure to light before the re-development.

Option #2. I'm not expecting miracles, I'm more using this as an opportunity to try things out for such an occasion as I screw something up that actually matters and then I had a bleaching hiccup.

fump · Apr 3, 2023

Doremus Scudder said:
If you get no bleaching of an untoned negative, then your bleach is not working. That said, selenium-toned negatives may not respond well to bleaching, especially if they have been strongly toned for intensification.

I use a ferricyanide/bromide rehalogenating bleach. I use 15g potassium ferricyanide and 15g potassium bromide per liter of water, but the amounts and proportions are not that critical. The bleach should last for a fairly long time if not contaminated (e.g., with fixer, which kills bleach really quickly). I have a bottle just for bleaching negatives that's been going for a few years now.

You bleach with the lights on so you can watch the process. Bleach until the image is completely gone, except for maybe a very faint ghost of an image. The resulting silver bromide in the emulsion has been well-exposed to light since you did the whole process with the lights on. If you didn't (e.g., did everything in a tank), then, yes, you need to expose the film to light. If the film is on a reel, I'd take it off and hold it up to the light to make sure it was well and evenly exposed and then re-spool it.

Now simply redevelop in your staining developer of choice (PMK is mine) for a bit longer than your normal developing time for that film/developer combination. You can't overdevelop; you want the silver bromide to all develop to completion.

While Sirius is correct that what was not recorded on the film can't be retrieved, sometimes bleach/redevelop can give a gratifying boost to shadow detail.

Hope this helps,

Doremus

It's reassuring that, other than the bleach not doing anything, I had the rest of this mess right. Hopefully it'll be another tool I can pull out to salvage something sometime.

john_s · Apr 3, 2023

I did a toning course run by Tim Rudman years ago, and he showed us an interesting print. A dense print had been toned in selenium toner, then bleached to remove metallic silver, the resulting print being an amazing reddish-brown. My take from that was that the selenium part of the image was unaffected by a standard bleach, as Gorbas suggested in his post above.

Sirius Glass · Apr 4, 2023

I found that if I could not bring the image out with Selenium the photograph was not usable and moved on.

pentaxuser · Apr 4, 2023

fump said:
It's reassuring that, other than the bleach not doing anything, I had the rest of this mess right. Hopefully it'll be another tool I can pull out to salvage something sometime.

If you are sure you had freshly made the bleach with active ingredients in the way you state then I can think of no reason why it didn't bleach

Have you tried making the bleach again and trying again or at least testing it?

pentaxuser

Bleaching thin negatives to redevelop in Pyro

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