Swapping B&W reversal process chemicals

I was planning to process some B&W slides using the steps outlined here: (there was a url link here which no longer exists)

I've sourced all the chemicals apart from potassium dichromate, which is proving hard to track down in the UK. Also after reading about the effects on health of this powder, I'm wondering about changing the bleach step.

I have two questions for the chemists out there:

1. Is it okay to swap the bleach from another B&W reversal process? For example, Ilford's suggested bleach requires potassium permanganate and sulphuric acid. I'm aware of the dangers of the latter, by the way, and of the potential explosive nature of the two when mixed in high concentrations.

The bleach seems to be a stand-alone process, not affected by or affecting any other step, so assuming it is okay, the next question is:

2. As I've already bought the sodium bisulphate, could this be used instead of the sulphuric acid in part B of the bleach, together with potassium permanganate for part A? I'm guessing the answer to this is no, but I thought it was worth asking in case I already have chemicals I could use.

Hi, I'm new here.

1 - Yes you can definitely use whatever bleach you want. It's purpose is simply to remove developed silver. It doesn't interact in any way with other chemicals. I've used the permanganate - sulph. acid bleach many times, with success. It has a great advantage of being only corrosive, but not toxic (unlike dichromate). The only thing you've got to be aware of is that this bleach severely softens the emulsion, and you have to be careful not to scrape your emulsion off the film. Don't worry about the explosive nature of the two, just remember NEVER to mix dry permanganate with acid, always do it in a water solution. Tip: you can make two separate solutions of permanganate and acid, and store them in separate containers, then mix the amount you need just before bleaching. The separated solutions can be stored forever. Mixed and used bleach should be discarded.

2 - I guess no. You need sulphuric acid.

Mat1024 said:

Hi, I'm new here.

1 - Yes you can definitely use whatever bleach you want. It's purpose is simply to remove developed silver. It doesn't interact in any way with other chemicals. I've used the permanganate - sulph. acid bleach many times, with success. It has a great advantage of being only corrosive, but not toxic (unlike dichromate). The only thing you've got to be aware of is that this bleach severely softens the emulsion, and you have to be careful not to scrape your emulsion off the film. Don't worry about the explosive nature of the two, just remember NEVER to mix dry permanganate with acid, always do it in a water solution. Tip: you can make two separate solutions of permanganate and acid, and store them in separate containers, then mix the amount you need just before bleaching. The separated solutions can be stored forever. Mixed and used bleach should be discarded.

2 - I guess no. You need sulphuric acid.

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Thanks for the info, particularly the note about the emulsion softening. I was planning to carry out a chemical reversal rather than remove the film from the reel, so I guess that is less of a problem?

No need to remove film from reel when re-exposing.

I had emulsion slide off some films when using permanganate bleech. I now use Moersch's Potassium Dichromate bleech which comes in liquid form and available in Ireland here: http://www.thephotoshop.ie/index.php?route=product/product&path=69_94&product_id=408

as far as I know, the acid is specific to the other half of the bleach so you cant mix and match. all the chems just need to be handled with care and be careful and smart. there should be no issues.

chem reversal is the way to go in my mind. keeps things simple and easy. i did half the bleach amount so the emulsion did not sluff off. just doubled the time. have never had an issue with it. and Mr. red (peter C), whom i borrowed the formula from, has never had an issue either.

its not that hard once you do it once. just make sure to used distilled water for the iron out stage!

john

here is a quote from Peter regarding the acid.

"Note: You cannot use any acid here. It's not the fact that it is an acid that is at work. It's food for the dichromate or permanganate reaction (H3O+) that will not alter the how the dichromate or permanganate works. Sodium BiSulfate works, but I have no info on the amount to use."

"
Replacement for Sulfuric Acid

Some of my buddies over on apug helped me find a reference for Sodium Bisulphate. 25g in 1l should be adiqute for this use.

The high side, it should be available ant most home brew supply store and pool dealership."

I use Sodium Bisulphate with dichromate as mentioned in my post. i get the bisulphate at a pool store.I am lucky as my local photo store stocks many photo formulary chems and they have dichromate in stock, so no shipping issues

john

I have used Sodium BisulphAte with dichromate, works well. The last Dichromate I got was from OxfordChemserve.

1. You can use permanganate reversal in place of dichromate. Just keep in mind three things : (a) Use sodium metabisulfate as clear with permanganate while one has to use sodium sulphite with dichromate bleach. (b) always prepare permanganate bleach fresh otherwise solids with form in the solution and possibly get deposited on film. Dichromate on the other hand keeps forever. (c) permanganate bleach softens the emulsion, so you should use hardening fixer or a separate hardening bath and be cautious with film handling before hardening. Too much time in permanganate bleach might soften emulsion to the point that there will be pinholes in or it might even slide off the base. Dichromate bleach hardens the emulsion.

P.S. I have only used permanganate bleach myself.

2. I have no experience with using sodium bisulfate but I have seen people use it with success. However, using sulfuric acid is not that difficult. You can use car battery acid which is 37-38% sulfuric acid. Always use nitrile rubber gloves while handling the acid.

You have already read ilford pdf. I suggest you read Dead Link Removed too.

Sodium Dichromate will work too.

Bisulphate works.


The problem with permanganate is that it easily damages the film in the process. Where as dichromate is reliable and you can leave the film in there and no real danger of over doing it.

I planned on trying Iron (III) Oxide at some point, since it'll dissolve in dilute acid solutions. Not sure if it'd work, but thought I wanted to try it out.

hi fujilove
you might also look at this article
http://unblinkingeye.com/Articles/PBR/pbr.html

have fun reversing !
john

destroya said:

as far as I know, the acid is specific to the other half of the bleach so you cant mix and match. all the chems just need to be handled with care and be careful and smart. there should be no issues.

chem reversal is the way to go in my mind. keeps things simple and easy. i did half the bleach amount so the emulsion did not sluff off. just doubled the time. have never had an issue with it. and Mr. red (peter C), whom i borrowed the formula from, has never had an issue either.

its not that hard once you do it once. just make sure to used distilled water for the iron out stage!

john

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Thanks John - I managed to get hold of the Iron Out, so definitely going to use chemical reversal. Thanks for the tip regarding using half strength/double time bleach. I'll keep that in mind.

I managed to get hold of the chemicals for the bleach this week, so apart from the Dektol, I'm good to go.

I've been pondering the comments about the bleach softening the emulsion to the point where it can come away from the base. I was planning to run the process using my Jobo CPP2, but now I'm having visions of the rotary agitation being too strong and not helping in this regard. Am I being paranoid?! Anyone else using a Jobo, or should I be doing this manually as I do with my B&W negatives?

Jobo rotation is not going to make any negative impact as long as you keep the time to 3.5-5 min. Longer than that and you have problems with/without Jobo.

davedm said:

Jobo rotation is not going to make any negative impact as long as you keep the time to 3.5-5 min. Longer than that and you have problems with/without Jobo.

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Thanks...thought I was being paranoid. I've just read Jens Osbahr's process PDF and I can see he also recommends a Jobo.