DICHROMATE VS PERMANGANATE FOR REVERSAL BLEACHING

Having failed in the past to use potassium permanganate to process Tri-X 7266 and Fomapan R100, I've been using potassium dichromate + sulphuric acid instead with great results. The biggest drawback for me is the toxicity of dichromate; I just feel really uncomfortable using this stuff. Which leads me to give permanganate another go PLUS sulphuric acid as suggested by ILFORD. I didn't add sulphuric acid in the past.

http://www.ilfordphoto.com/Webfiles/20061291034093.pdf

A friend said it works great with Tri-X, but doesn't know if this will work with Fomapan R100 or ORWO UN 54.

Anyone have any experience with the permanganate recipe with Fomapan or ORWO UN 54?

pdelrosario said:

Which leads me to give permanganate another go PLUS sulphuric acid as suggested by ILFORD. I didn't add sulphuric acid in the past.

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Why not? All these potassium-x-manganate bleaches require sulphuric acid!

pdelrosario said:

A friend said it works great with Tri-X, but doesn't know if this will work with Fomapan R100 or ORWO UN 54.

Anyone have any experience with the permanganate recipe with Fomapan or ORWO UN 54?

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The recipes for developing reversal B/W films are almost universal; they only differ on the duration (and temperature) of the first developer bath. The bleach then fully removes the developed (metallic) silver, the light-reexposure needs to be enough to fog the film (but doesn't need clinical precision), the second developer develops to completion (fully), so again not critical in times, and fixer should remove any left traces of non-developed silver.

Don't forget to use the clearing baths in between.

The formulas for reversal development are all over this forum.

It should work correctly with Fomapan R100, Orwo and practically all B/W film that is reported to work correctly with the reversal process. Again, you will have to experiment with the first developer times and perhaps with the bleach times.

Disclaimer: I'm just an "armchair specialist" at this. I never attempted B/W reversal (laugh)... Because it isn't easy to source either dichromate or permanganate here.

FYI
The processing kit for Fomapan R100 does use a permanganate bleach. (Permanganate + acid, stored separately)

The Ilford method works quite well IF YOU FOLLOW THE DIRECTIONS. Unless the bleach solution is acidic the bleaching may not be complete AND there is a good chance that manganese dioxide (a black solid) will be deposited in the film.

Please read the following MSDS for potassium dichromate. You will find that the main problem is with ingesting the chemical. By wearing gloves you prevent any skin irritation and adsorption from that route. When working with the solid wear a dust mask and goggles. It is safe to work with if you follow the precautions. The bleach solution is quite dilute and does not pose any serious risk. Used solutions should be disposed of as toxic waste after a bit of sodium sulfite is added to reduce the chromium to the trivalent state which is much less toxic. The solution will change from orange to green..

http://dragonseye.com/holography/MSDS/PotassiumDichromate.pdf

Well I guess potassium permanganate bleach works with any film. It just has a very very short lifetime as soon as the sulfuric acid is added.

So I add the sulfuric acid to the permanganate not before the film is in the stop bath and transfer the film immediately.

There is enough time to mix up the bleach before you start processing. Attempting to do so while processing film is an invitation to screw up. Film development bears a resemblance to French cooking. Everything should be assembled BEFORE you start. The French call it mise en place "everything in its place."

Gerald C Koch said:

There is enough time to mix up the bleach before you start processing. Attempting to do so while processing film is an invitation to screw up. Film development bears a resemblance to French cooking. Everything should be assembled BEFORE you start. The French call it mise en place "everything in its place."

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Oh, don’t worry everything is in place before I start. I just have to pour the sulfuric acid in the permanganate.

I never screwed up anything with this method. BTW Fotoimpex recommends exactly this method for the Foma reversal kit.

Gerald C Koch said:

There is enough time to mix up the bleach before you start processing. Attempting to do so while processing film is an invitation to screw up.

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I can not emphasize this enough. Potassium Permanganate has an excellent sensor for hurry and stress, and will dissolve ridiculously slowly when you wait for it.

I double checked the Ilford instructions for the bleach solution. Nowhere does it say the permanganate and sulfuric acid solutions have to be mixed the very second before use. Mixing before starting your processing is perfectly fine. When you are in the middle of processing film you have enough to do without handling two dangerous chemicals. What Ilford or Foma does not want is for people is to store mixed bleach. Foma's instructions are "Do not store solved (thinned) solutions!" This is what is meant by their use of the word 'immediately'. Unfortunately translation into English is not always smooth.

Gerald C Koch said:

I double checked the Ilford instructions for the bleach solution. Nowhere does it say the permanganate and sulfuric acid solutions have to be mixed the very second before use.

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IIRC the Ilford instructions contain a bath which sort of clears up leftover MnO2. Since not every set of instructions for B&W reversal contained such a step, I could imagine some sets being more hysterical about the bleach being fresh than others.

Ilford instructions have metabisulfite clearing Bath after bleach and lots of wash steps.

Rudeofus said:

IIRC the Ilford instructions contain a bath which sort of clears up leftover MnO2. Since not every set of instructions for B&W reversal contained such a step, I could imagine some sets being more hysterical about the bleach being fresh than others.

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The problem with some metal oxides is that their solubility decrease rapidly with age. It is therefor preferable to prevent the manganese dioxide formation in the first place. Therefor the bleach needs to be acidic. Then too if the bleaching is stopped by the formation of manganese dioxide then the full bleaching potential is lost.

I have worked with potassium dichromate for over 50 years...still here and still healthy. Wear gloves, no fast jerky moves, be steady and you will be ok.

Gerald C Koch said:

I double checked the Ilford instructions for the bleach solution. Nowhere does it say the permanganate and sulfuric acid solutions have to be mixed the very second before use. Mixing before starting your processing is perfectly fine. [...] What Ilford or Foma does not want is for people is to store mixed bleach. Foma's instructions are "Do not store solved (thinned) solutions!" This is what is meant by their use of the word 'immediately'. Unfortunately translation into English is not always smooth.

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For what's worthing, when I do reversal of enlarged negative (as I wrote here there was a url link here which no longer exists), I store mixed permanganate bleach, in "high" concentration ( 50g KMn04 /L - according Lawless article), in a well stopped brown bottle, since weeks. Even what I called "stage I" dilution (the above 1+9, 5g/L) seems to keep long, the same way.

The "stage II" solution, where I dilute the previous 1+4, and completing with fresh sulfuric acid, is reusable a few days before sedimenting.

So I presume bleach keeping properties are related to it concentration...