BW reversal bleach failure

Anon Ymous · Mar 21, 2017

Yesterday I made an attempt at bw reversal and as the title says, the bleaching stage failed. I used 500ml of permanganate bleach, which was mixed just before the bleaching stage. 0,5g of potassium permanganate was dissolved (or so I thought) in ~200ml deionised water and 22g of sodium bisulfate in ~300ml. These solutions were combined just before bleaching, as I mentioned earlier. Previously I had tried a 250ml batch of such a bleach with a piece of already processed, bullet proof leader and it worked nicely. This bleach is similar to the one proposed by Ilford, but with half the concentration of permanganate and bisulfate instead of sulfuric acid. All processing steps were done at 20°C and I bleached for 5'. I didn't invert the tank during bleaching, but used a swirling motion for the whole 5'. This is what the film leader looks like at the fully exposed - fully unexposed section:

This clearly shows that bleaching was incomplete and the spots were probably caused by undissolved potassium permanganate. So, the two questions are:

1) How do you guys make sure the permanganate has fully dissolved? The solution is too dark to spot any chunks and I'm not sure that filtering permanganate solutions is a very good idea.

2) For how long do you bleach? In this occasion the bleach might have been too weak given the undissolved permanganate and I can probably have a look at the film during bleaching, but your experience would be welcome.

Thanks in advance!

pdeeh · Mar 21, 2017

It's not necessarily Undissolved permanganate. (it could be manganese dioxide)
Did you use an acidic clearing Bath (usually sodium metabisulfite) after bleaching?
It may be that your bleach is not sufficiently acidic, but I have no experience with using bisulfate rather than sulfuric acid.
I'm sure Rudeofus or Gerald Koch will drop by and set you right soon.

Anon Ymous · Mar 21, 2017

pdeeh said:
It's not necessarily Undissolved permanganate.
Did you use an acidic clearing Bath (usually sodium metabisulfite) after bleaching?

Oh, yes I did. 12,5g metabisulfite in 500ml water, 2' continuous agitation and it worked well. These spots are more evident in the beginning of the film, which is nearer the center of the reel. There are very few if any at all at the end of the film. The swirling motion I used gathered any undissolved solids towards the center of the reel, just like a vortex would do.

ruilourosa · Mar 21, 2017

dicromate and sulfuric acid! permanganate is always a mess

Anon Ymous · Mar 21, 2017

ruilourosa said:
dicromate and sulfuric acid! permanganate is always a mess

I know, it's far more reliable, it's safe if handled properly, but I'd rather not use dichromate.

chrisaisenbrey · Mar 21, 2017

You can dissolve the permanganate the previous day or prepare it as a stock solution. I use a 2% stock solution. As long as there is no sulfuric acid (or bisulfate) it is stable over weeks.

But I also wonder it the problem is undissolved permanganate.

You can inspect the film during bleaching and clearing, with not too bright light.

LAG · Mar 21, 2017

Anon Ymous said:
1) How do you guys make sure the permanganate has fully dissolved? The solution is too dark to spot any chunks and I'm not sure that filtering permanganate solutions is a very good idea.

2) For how long do you bleach? In this occasion the bleach might have been too weak given the undissolved permanganate and I can probably have a look at the film during bleaching, but your experience would be welcome.

Thanks in advance!

1.) I always prepare everything well mixed & with warm water in advance, never a problem. Were the chemicals in a good condition?

2.) 3 minutes (agitated constantly and with determination) - but I'm afraid my numbers won't help you

ruilourosa said:
dicromate and sulfuric acid! permanganate is always a mess

My advice too!

flavio81 · Mar 21, 2017

Hi Syd,

Why aren't you using sulfuric acid?
It can be bought as "battery acid".
It is dangerous to the skin but it is not toxic.

Anon Ymous · Mar 21, 2017

LAG said:
1.) I always prepare everything well mixed & with warm water in advance, never a problem. Were the chemicals in a good condition?

The bisulfate is slightly off white granules and gives crystal clear solutions. The permanganate is probably old and was given to me by a chemist friend. He used to work at a lab where they refreshed some of their chemicals and dumped old stock. It is analytical reagent grade, Mallinckrodt branded.

It seems that it's not that uncommon to have some undissolved permanganate. Jens Osbahr in his reversal process document (page 19) states "Pour out the bleach into the bottle very slowly to achieve that crystals which are still not dissolved remain in the Erlenmeyer flask."

flavio81 said:
Hi Syd,

Why aren't you using sulfuric acid?
It can be bought as "battery acid".
It is dangerous to the skin but it is not toxic.

I've got both, but it shouldn't matter anyway. I used bisulfate because the sulfuric acid I have seems to have some kind of contamination floating at the top.

Rudeofus · Mar 21, 2017

I have had very similar looking stains when I processed B&W reversal for the first time, and I am quite confident that undissolved Potassium Permanganate is the culprit. There are two ways IMHO to avoid this:

Follow chrisaisenbrey's advice and dissolve the Potassium Permanganate well in advance to make sure it is fully dissolved by the time you use it
or, for the impatient like me: mix fresh, but filter the Potassium Permanganate solution before use. A simple coffee paper filter will do.

Since I filtered my Potassium Permanganate, I have not had these stains, and my stash of Potassium Permanganate is several years old and looks odd - but still works!

Anon Ymous · Mar 21, 2017

Ah, thanks Rudi, coffee filter it is then.

Anon Ymous · Mar 22, 2017

Alessandro Serrao said:
The problem is that you didn't invert the tank.
Inverting the tank will solve your problem.

So, more vigorous agitation is needed? I'll keep that in mind, thank you.

Rudeofus · Mar 23, 2017

Alessandro Serrao said:
The problem is that you didn't invert the tank.
Inverting the tank will solve your problem.

Agitation is essential, but won't solve Anon Ymous's spot issue. I have a strip of B&W reversed film just like that, and agitation certainly was not the issue. These spots never showed up again since I started filtering my bleach.

Anon Ymous · Mar 23, 2017

Rudeofus said:
Agitation is essential, but won't solve Anon Ymous's spot issue. I have a strip of B&W reversed film just like that, and agitation certainly was not the issue. These spots never showed up again since I started filtering my bleach.

I think Alessandro means that the horizontal dense part that didn't clear during bleaching wouldn't be there if I used more vigorous agitation.

Rudeofus · Mar 23, 2017

AFAIK the bleaching process runs to completion, if bleaching appears incomplete, you should at least double bleach time.

Anon Ymous · Mar 26, 2017

Another attempt, another failure, but not bleach related this time.

Above you can see a quick scan of a problematic frame. Not all frames have such spots, but these appear (and ruin) at quite a lot of the frames. But let me describe my processing workflow, whose steps were all done at 20°C. The film was expired (~5 years) 400TX. Has kept very well and doesn't really seem to have lost speed, nor gained significant fog.

1) Presoak for 2'.
2) Develop for 8' in D67 (D19 + 2g/l Potassium Thiocyanate).
3) Wash with 4 water changes and generous agitation.
4) Bleach with 1g/l Potassium Permanganate and 50g/l Sodium Bisulfate. This time the bleach solution was filtered and agitation was more vigorous, with inversion. I had a sneak peek at 3' (incomplete bleaching) and at 5', where bleaching seemed to be complete. I bleached for 2' more, for a total of 7'.
5) Metabisulfite (25g/l) clearing bath for 2'. Film cleared nicely.
6) Wash with 4 water changes and generous agitation.
7) Exposed film while on reel for 90'' from each side, 20-30cm away from a 75W lamp.
8) Develop in D76 1+2 for 15'. A normal development time for such a dilution would be ~12', so I gave it 25% more. I inspected the progress of development twice in full light where I also took photographs. Could the developer droplets on the film when I was inspecting development have caused the denser spots?
9) Stop.
10) Fix in F24.
11) Wash.

Any ideas about what caused the spots? By the way, the clear film leader also seems to have such spots. In case you're wondering, these spots were not caused by the wetting agent.

Thanks in advance.

LAG · Mar 26, 2017

Anon Ymous said:
... Any ideas about what caused the spots?

Did you see the marks before or after the second developer?

I can see not only water marks, but air bubbles. IMHO those marks are due to various reasons (and not only with reversal) as you already know: hard water and/or washing steps (three marks in the center of the image and other places), developer stage and/or clearing bath & air bubbbles (upper right in the image, one big and two small near, and in other places) ...

My clearing bath is always 3 min (at least). I'd also dare to say that steps 3 to 6 should be done with continuous agitation, it's up to you of course.

Anon Ymous said:
Could the developer droplets on the film when I was inspecting development have caused the denser spots?

No.

I always continue the process to open light after "your 6 step", and I've made photos and videos, but never "with flash"? (Did you use one?), anyway that was not the reason.

Best of luck next time!

Anon Ymous · Mar 26, 2017

@LAG

Close inspection of the film didn't reveal any watermarks. Generally speaking, I don't have any serious problems with watermarks, I use deionised water with few drops of Photo Flo 200 and it works very well for me. Now, regarding air bubbles, I've never had such a problem with them, I always hit the tank on the bench and it seems to dislodge any bubbles. Of course, this doesn't mean that it can't be the cause of the spots. If these are air bubbles they have to have happened during the first developer, because they're denser than the surrounding area. To be honest, I think bubbles (air bells?) would have caused an effect that wouldn't be that sharp, but more gradual. Oh and I only spotted them when I hanged the film to dry.

Steps 3 - 6 had continuous, generous agitation and film looked gray after the clearing bath. I also didn't use any flash when photographing the process. I mentioned the developer droplets on the film while it was out of the tank as a cause because it could have given it some time to act locally (and create these denser spots), but then it was only for seconds in a 15' step. That's a tad too little for such an obvious effect.

Gerald C Koch · Mar 28, 2017

Anyone mixing up their own solutions should invest in a box of lab grade filter paper. You want the coarse or fast type. Don't buy the quantitative analysis or ashless grade as it not necessary and much more expensive. Ordinary coffee filters will not work as they are designed for coffee grounds and nothing finer. Then learn how to fold the paper correctly. There is an explanatory video on the web.

Rudeofus · Mar 29, 2017

The second developer must develop all the silver it can find, and I am not entirely sure whether "Develop in D76 1+2 for 15'" does this. Therefore differences in total development time will show up as spots and stains. If you absolutely want to take a look at the strip in between, do the following instead of your step 8:

Put in second developer
When impatience overcomes you, pour developer into a jug, immediately fill tank with stop bath. Any stop bath will do, and you can reuse it.
Then do a brief water rinse, 2-3 water changes should suffice
Then look at the sample as long as you want
Proceed with step 1 until second development is complete

Anon Ymous · Mar 29, 2017

Rudeofus said:
The second developer must develop all the silver it can find, and I am not entirely sure whether "Develop in D76 1+2 for 15'" does this...

Me neither. I'll probably make some D19 for my reversal tests. Adding few ml of KSCN solution will turn this to D67 for use as a 1st developer, while keeping the rest for use as a second developer. Perhaps 8' in D19 is ok, but 10' wouldn't hurt, would they?

Meanwhile, 2g/l of KSCN in D67 doesn't seem to clear the highlights enough. Perhaps I should increase KSCN by 50% and see what happens? And prolonging 1st development time to 9' from 8' would give me a bit more contrast, while clearing the highlights a bit more. For the record, EI200 and EI400 shots are the ones with enough retained detail, but highlight density is high, especially for EI400.

Rudeofus · Mar 29, 2017

If you add increasing amounts of SCN- to FD, you get higher contrast and higher fog, which translates into brighter highlights and less black shadows. If your shadows regions are not dense enough, either reduce SCN-, or add Br-. Here is how I would go at this (assuming your bleach and second developer really work to completion as they should):

aim for an FD time of about 10 minutes +/- a few minutes
if highlights aren't clear after 10 minutes, add SCN- in 0.5 g/l increments until highlights are as desired
if shadows become too bright in the process, add Br- in 0.5 g/l increments

Adding Br- may darken your highlights a bit, increase FD time in 1 minute increments to address this. With this procedure you should have good slides with relatively few iterations.

Rudeofus · Mar 29, 2017

PS: In E6, the second developer also has strong solvent in it to make it faster. You should be able to do this for B&W slides as well, to avoid second developer time from becoming excessively long.

Anon Ymous · Mar 29, 2017

Rudeofus said:
If you add increasing amounts of SCN- to FD, you get higher contrast and higher fog, which translates into brighter highlights and less black shadows. If your shadows regions are not dense enough, either reduce SCN-, or add Br-. Here is how I would go at this (assuming your bleach and second developer really work to completion as they should):

aim for an FD time of about 10 minutes +/- a few minutes

if highlights aren't clear after 10 minutes, add SCN- in 0.5 g/l increments until highlights are as desired

if shadows become too bright in the process, add Br- in 0.5 g/l increments

Adding Br- may darken your highlights a bit, increase FD time in 1 minute increments to address this. With this procedure you should have good slides with relatively few iterations.

Interesting information, thank you! My 8' 1st developer time is the upper limit of what is proposed as a starting point for D67 (6' to 8'). This resulted in somewhat soft contrast, but not too soft. The biggest problem was overall density, which made highlights denser than what they should be. I use some E6 slides I have as a point of reference for overall density. Increasing 1st developer time to 9' should probably do the trick, especially if 0,5g/l more KSCN will increase contrast by itself.

Rudeofus said:
PS: In E6, the second developer also has strong solvent in it to make it faster. You should be able to do this for B&W slides as well, to avoid second developer time from becoming excessively long.

Uh, E6 colour developer has a tiny amount of sulfite and this leaves us with KSCN as the only other solvent present. So, are you suggesting that adding some KSCN to the 2nd developer would reduce development time? Hmmm, if that's the case, perhaps I could reuse my 1st developer?

Anon Ymous · Mar 29, 2017

By the way, how exactly does thiocyanate work in bw reversal? I know thiosulfate is practically fixer and removes unwanted silver halides that would later form silver, thus making highlights too dense, but I'm clueless about thiocyanate.

BW reversal bleach failure

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