Troubleshooting permanganate bleach for reversal

adelorenzo · Oct 31, 2017

My first attempt at reversal processing tonight and my bleach step didn't work. The negatives had turned slightly creamy but still plenty of silver on there after five minutes. I realize now I should have kept bleaching but I didn't check them until after they had been through the clearing bath and exposed to light.

The negatives were FP4 exposed at ISO 50 and developed in Kodak D-11. Since they didn't bleach I can confirm that they looked quite good as negatives.

My choice of bleach was determined by what chemicals I had on hand so I used a formula that called for equal parts potassium permanganate (4g/L) and sodium bisulfite (34.5g/L). I substituted equal weight of sodium metabisulfite which the darkroom cookbook says is OK.

I searched some old threads on this topic and there seem to be a few possibilities.

More sodium bisulfite, less permanganate
Use sulfuric acid instead of the bisulfite (Ilford formula)
Use a dichromate bleach but I only have ammonium dichromate and all the formulas call for potassium dichromate

I'm leaning towards option 2 but would love to get some thoughts. I have also learned that I need to bleach to completion no matter what.

Fraunhofer · Oct 31, 2017

Based on my limited understanding of chemistry, I would not expect number 2 to make a difference.

Anon Ymous · Oct 31, 2017

Every permanganate bleach formula I've seen uses sulfuric acid, or sodium bisulfate, not bisulfite. Sodium bisulfate is practically half neutralised sulfuric acid. Bisulfite should be used for the clearing bath after the bleach. So yes, option #2 is what you should have used in the first place. Before committing any serious work to it, do a test run with a small, fully exposed piece of film. This will tell you how well your process works.

Rudeofus · Oct 31, 2017

Despite the common notion about "Sulfite is a silver solvent": it isn't, in fact, Silver Sulfite is quite insoluble, and only small amounts of silver are complexed by Sulfite if there is a massive surplus of Sulfite. I would therefore guess that the Silver Sulfite stayed in your emulsion and was then developed by the second developer. There are few soluble silver salts: Silver Acetate, Silver Nitrate and to some extent Silver Sulfate. Acetate anion may not be stable in the presence of Permanganate, and Nitric Acid is not a pleasant compound to have near you, therefore you're basically down to Sulfuric Acid or, as suggested by Anon Ymous, Sodium Bisulfate.

Fraunhofer · Oct 31, 2017

Yes on the sodium bisulfate, should have read more carefully..

removed account4 · Oct 31, 2017

I. can’t quite put my finger on them or I would post links here
But go to the unblinking eye website and look for an article by h yurow. He has the exact formula. Also poke around the lf site about a year ago someone who regularly uses the formula you are attempting posted additional info.. good luck

destroya · Oct 31, 2017

I use #3 and have never had any issues. I chose 3 because some people had issues using permanganate. but now its real hard to get dichromate

Photo Engineer · Oct 31, 2017

Do not use any Ammonium salts in a B&W reversal bleach of any type.

PE

adelorenzo · Oct 31, 2017

Thank you everyone for the replies. Good catch, it was the fact that I needed to use sodium bisulfate in the bleach and not bisulfite. I figured it might be something simple. I did think it odd that the bleach and the clearing bath were using the same chemicals.

I think I can get sodium bisulfate in the pool chemicals section over at the Canadian Tire. Will try that next time.

studiocarter · Oct 31, 2017

destroya said:
I use #3 and have never had any issues. I chose 3 because some people had issues using permanganate. but now its real hard to get dichromate

I recently bought a pound from Photographers Formulary

sushi · Feb 14, 2018

Might be a bit late, but in case you still reversal process using permanganate bleach: add 20g/l of Calgon-Photo and it will last basically forever. I have a bottle of permanganate bleach stabilized this way that I mixed over a year ago, and it bleaches like a champ. That way you won't need to discard you bleach after use.

guangong · Feb 14, 2018

The general opinion shared by those who process reversal movie film is to avoid using permanganate in the bleaching process. Other formulas have their fans but permanganate is usually avoided.

Rudeofus · Feb 14, 2018

The Foma reversal kit uses Permanganate, so this proclaimed consensus may not be as wide spread. I have done B&W reversal with Permanganate, both with Foma's kit and with homebrew formula, and it worked well (assuming I completely dissolved all of the Permanganate).

revdoc · Feb 16, 2018

Permanganate bleach is fine. It can soften the emulsion, but that's something you can manage with careful handling.

Permanganate is also the only thing doing the bleaching in a permanganate bleach. Generally an acid is added to prevent the formation of manganese dioxide particles in the emulsion, but that's all the acid is there to do. The unfortunate side effect is that the acid reacts with the permanganate, destroying both. This is why the bleach only lasts a short time after you mix the two components.

guangong · Feb 16, 2018

Rudeofus said:
The Foma reversal kit uses Permanganate, so this proclaimed consensus may not be as wide spread. I have done B&W reversal with Permanganate, both with Foma's kit and with homebrew formula, and it worked well (assuming I completely dissolved all of the Permanganate).

I processed three 100ft rolls of Fomapan on three different occasions, following formulas on their web page ( kits not available in US at the time) and I was not satisfied with results. Returned to my sulfuric acid dichromate formula with D19. For me, and many who process 16mm movie film, this is a tried and true processing method. Also, the last time I checked, Kodak 16mm film is cheaper than Foma.
I do use potassium permanganate to treat my tropical fish when needed.

Rudeofus · Feb 16, 2018

Can you elaborate what you mean with "not satisfied with results" ?

Photo Engineer · Feb 16, 2018

revdoc said:
Permanganate bleach is fine. It can soften the emulsion, but that's something you can manage with careful handling.

Permanganate is also the only thing doing the bleaching in a permanganate bleach. Generally an acid is added to prevent the formation of manganese dioxide particles in the emulsion, but that's all the acid is there to do. The unfortunate side effect is that the acid reacts with the permanganate, destroying both. This is why the bleach only lasts a short time after you mix the two components.

Sulfuric acid is necessary in order to form Silver Sulfate which dissolves into the bleach bath or otherwise washes out. If another acid were to be used, you would not get a clear reversed image.

PE

studiocarter · Feb 16, 2018

I have a one pound bottle of Chrome Alum from Photographers Formulary. How many grams of it should I put into one liter of water to harden Fomapan R 16mm 2R film before using Permangate as a developer?
Thanks.

Photo Engineer · Feb 16, 2018

I use a 10% solution which would be 10 g in a total of 100 ml. Start with 800 ml of water and add 100 g of the Chrome Alum. Dissolve and slowly add water up to 1 L. I treat for 5 minutes and then give it a 5 minute wash. However, IDK if this is the optimum hardener for your situation. I would normally use a formalin prehardener.

PE

studiocarter · Feb 17, 2018

Thank you for that. Now I have to groan because I do not have any Formalin. Looking it up, it is sold to heal tropical fish. There are different concentrations. 37 percent and 10 percent. Maybe more different ones. How do you use it?
Thanks.

Photo Engineer · Feb 18, 2018

Here is a prehardener formula:

Water 800 ml
Formalin 37% 3 - 10 ml (depending on hardness of starting film and temperature of process)
Sodium Sulfate 100 g
Adjust pH to 8 - 9 at 20C
Water to 1L

Treat 5 minutes at 20C, wash 10 minutes at 20C

Continue normal process

PE

Rudeofus · Feb 18, 2018

studiocarter said:
Thank you for that. Now I have to groan because I do not have any Formalin. Looking it up, it is sold to heal tropical fish. There are different concentrations. 37 percent and 10 percent. Maybe more different ones. How do you use it?

When I went to our local chem supplier and asked for "the highest concentration of Formalin you will happily sell to an amateur with no dedicated lab", they gave me 20% Formalin. Since Formaldehyde is a gas, I would expect 37% to smell much stronger than my 20% solution.

studiocarter · Feb 23, 2018

PE,
I really appreciate how you answer questions and help everyone. Thank you very much.
Michael Carter

Photo Engineer · Feb 23, 2018

Thanks. I'm glad to help.

PE

Troubleshooting permanganate bleach for reversal

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