Potassium Permanganate Bleach - tiny white dots

[Jeremy Saint-Peyre]

Hello folks,

First things first : i do not have any dichromate on hands and if i could i wouldn't because of the toxicity.

That being said, i'm experiencing trouble with my fomapan R100 processing, see those tiny white dots all around ? That's my problem...

Here is my workflow :

FOMAPAN R100 EXPOSED AT 100 ISO

- For every bath, continuous agitation on first minute then 10 sec each minutes.
- For every rinsing bath : 2 minutes running water.
- For every bath, temperature is 20°C
- Beside the two bleach solution mixed together just before use, Potassium Permanganate, Sodium Bisulfate and Sodium Metabisulfite bath are made the week before to ensure full dissolution in distilled water. Other bath are made with tap water. Fix bath is Agfa Fix Ag 1+5 (not Agfa Fix Ag Plus fixer)
- Since this test, i've tried replacing re exposure + second developper + fix with Sodium Hydrosulfite (60gr/film 135x36 concentrated at 13,2%, around 455ml). It worked, 12min30 bath and a lot less white dot, Dmax and overall density increased, but accutance and grey range isn't as great. I had to increase the first developper time to 12min.

So here it is :

1 – Pre soaking to bring the film at 20°C
2 – Processing in Rodinal 1+50 9min 20°C
3 – Rinsing
4 – Bleach : 250 ml Potassium Permanganate 0,4%
250 ml Sodium Bisulfate 10%
Mixed just before use, 8min at 20°C
5 – Rinsing
6 – Cearing : 500ml Sodium Metabisulfite 3%, 3min at 20°C
7 – Rinsing
8 – Re exposure, 30 seconde each side, reel moving in a white bucket full of water 1m from a 100W lightbulb. (Foma recommandation)
9 – Processing in Rodinal 1+50 9min 20°C
10 – Rinsing
11 – Fix, 1+5 5min 20°C
11 – Rinsing running water 10 min
12 – Distilled water final bath
13 – hanged to dry in the film cabin for 24h.

Any recommandation/solution is welcomed !

Have a nice day,

Jérémy

 

[Rudeofus]

The bleach is that one bath which does not appear in regular B&W processing, and it seems to be the bath most prone to problems. I had brown spots just like that when I tried to use freshly mixed Potassium Permanganate bleach - apparently some small bits of Potassium Permanganate dissolve very very slowly. In your case the week long storage of Potassium Permanganate could have led to formation of Manganese Dioxide or something insoluble, this could be the reason for your bright spots. Since Potassium Permanganate solution is dark colored and barely translucent, it is difficult to determine visually whether there is some precipitate in your bleach solution.

After experiencing these brown spots in my first B&W negatives, I started mixing my bleach an hour or two before processing starts, and filtering the bleach right before use in order to remove remaining bits of undissolved matter, and the resulting B&W slides came out nicely.

 

[Jeremy Saint-Peyre]

Thanks Rudeofus,

[QUOTE="storage of Potassium Permanganate could have led to formation of Manganese Dioxide[/QUOTE] even if it is only Potassium Permanganate + Distilled Water ?

I thought it was the reaction between Potassium Permanganate + Sodium Bisulfate that led to Manganese Dioxide. I also thought that the reaction between Potassium Permanganate + Sodium Bisulfate led to a quick exhaustion of the bleach, that why i used to mix it seconds before using it, but mixing a couple hour before use make no changes in efficacity and process time ?

Will try mixing 30min in advance and filtering right before use.

Any advice on the use/concentration/duration of first and second developper ?

Thanks !

 

[RauschenOderKorn]

Have a close look at the emulsion side of your film. Are the bright spots pinholes in the Emulsion?

If yes: you will find quite a few people reported (on various forums) emulsion peel-off after using this bleach. You can try to pre-harden the emulsion before processing.

 

[Jeremy Saint-Peyre]

Thanks RauschenOderKorn

For sure i can feel the white dots on my finger, it feels more like a ruggedness than pinhole... like something got caught in and wont leave. But i'll look again and closer. The density of the white dots is not the same through the film (the closer to the center of the reel the greater the density). I did thought about doing a chrome alum bath as a hardener, but after i increased the Sodium Bisulfate bleach's solution from 3,3% to 10% the emulsion wasnt soft anymore and the white dot density decreased even more when i switched to Sodium Hydrosulfite (60gr/film 135x36 concentrated at 13,2%, around 455ml) instead of a regular second developper.

 

[Rudeofus]

Potassium Permanganate is not overly stable in solution and usually precipitates brown Manganese Dioxide after a while. The Sodium Bisulfate essentially acts as a strong acid, which does not prevent the reduction from MnVII to MnIV, but does prevent formation of MnO2 precipitate. No idea what else could have formed in your Potassium Permanganate stock solution, but something apparently got into your emulsion and blocked the second developer. Since Sodium Hydrosulfite is a very strong silver ion reducer, the effect of this blockage was apparently reduced but not completely avoided.

There are a few things you could try as an experiment:

1. Put a test clip into your bleach for a few minutes, wash it and check for precipitate stuck in its emulsion. You can do this in room light.
2. Fully expose a test clip, then develop it in first developer, then repeat first test.
3. If at least the second test gives spots and bumps in your emulsion, try filtering the bleach and repeat the second experiment.
4. If you still get spots after third test, repeat the third experiment with freshly mixed and filtered bleach.

 

[RauschenOderKorn]

ike something got caught in and wont leave.

Just to be sure, we are talking about a positive film slide, right? So when you scan the pic you show us, you do not invert it, but it is a straight scan of the transparent film? When you speak about “greater density” of white spots, you mean there are more and they are bigger, or are you referring to a logD?

Particles on the emulsion usually appear as dark spots on a straight scan, no matter what colour they are. So if you can feel something with the finger, probably the emulsion has been damaged.

If chrome alum does not harden the emulsion sufficiently, you can also try the Moersch Hardener which is commercially available. Furthermore, you can try to reduce process time and or lower the process temperature in order to minimize the softening of the emulsion. You have that film in process for almost one hour. A well hardened film should be able to withstand that, but with poorly hardened film, it can cause problems.

 

[Jeremy Saint-Peyre]

Thanks Rudeofus, i'll try that and will include filtering in the work flow.

RauschenOderKorn : Yes, this is a positive black and white slide, meant to be processed as a slide. By greater density i meant greater in number per square cm, not logD, and the size remain quite the same.

I have some chrome alum left, how would you use it in density and time ? Is it a one shot bath ? I bought some lith chemistery from moersh not a month ago (i think so) damn it...

Wouldn't it interfere with the bleaching process if a harden the emultion before first developer ? (might be a silly question but i'm not that much of a lab rat)

 

[richyd]

Hi Jeremy
Are you sure it is from the permanganate bleach because I got excatly the same using dichromate bleach. This has happened with two films of the latest batch. With too many ongoing projects I just didn't have the time or inclination to investigate it. Batches of this film 2 or 3 years ago experienced a different marking issue and I assumed that this is an emulsion fault. The marks I get are not consistent on all frames.

 

[Jeremy Saint-Peyre]

@richyrd : no idea, never processed it in dichromate bleach, i'm doing test processing as a side project for little less than a year now and i've always experienced that issue. Because there is always more dot on the film at the center of the reel, and because there is less dot since i've switched to Sodium Hydrosulfite, i'm leaning to think taht thoses dots are Manganese Dioxide, so mixing a bit earlier and filtering will probably do it (i hope). Also, i think i should probably overdevelop a bit, to allow the bleach to work a bit more on that anti-halo layer (but i might be wrong).

@RauschenOderKorn : i've checked my latest test that also got white dot but a lot fewer, the film it smooth as hell, so two next step are filtering bleach and hardening the emulsion.

 

[SalveSlog]

Did you agitate the bleach continously? I think it is important to do so.

 

[RauschenOderKorn]

I have done some poking around in order to find some answers for you, hope this helps. (I have not done most of the below described on my own, so no guarantees)

1.) Permanganate Bleach / Reducer

The permanganate reducer (like your bleach, only half strength) has been quite common way back, but it seems it fell out of favour. Otto Croy describes the permanganate reducer in detail in his 1940 “Bild-Lehrbuch”, and he says that the ready mixed working strength solution has a long shelf live and can be used various times. He describes it to stain the film brown as manganese dioxide forms, but a clearing bath in potassiummetabisulfite (50g / l for 5 min.) will completely remove the stain (also the recommendation of Kodak in the June 1944 Formulary for the Ilford R.2), so will a prolonged acid fixing bath (recommendation of AGFA 1952).


2.) Hardening Baths

Different hardeners used to be quite common, either added to the developer (Orwo & Ilford), to the fixer or as a bath on its own. I was not able to find a formula for the hardener to be added to the developer, maybe somebody else knows more about that. Adding hardener to the fixer is rather late in your process, so I would use a hardening bath after the first development. The following formulas are recommended for film:

Agfa 405:
15 g chromealum
75 g Sodiumsulfate (cryst.)
Dilute in 1 l of water
Apply 3-5 min, make sure to agitate for at least the first minute, else you risk streaks on the film

If you prepare it at double strength, you made yourself some Kodak SB.4 Tropical Hardening bath, to be applied for 3 min.

Agfa 406
15 g chromealum
15 g Potassiummetabisulfite
Dilute in 1 l of water
Apply 3-5 min, make sure to agitate for at least the first minute, else you risk streaks on the film

TH-5 Hardener for film from the Film Developing Cookbook:
750 ml water
30ml Glutaraldehyde (25%)
20g Sodium Sulfite
2g Sodiummetaborate
Water to make 1 l

If in doubt if the bleach worked sufficiently after hardening the emulsion, you should be able to inspect the film at the end of the bleaching process without causing any problem.

 

[RauschenOderKorn]

PE has posted in a different forum the following formula for pre-hardener:

Quote----------------------------------

A simpler prehardener is as follows:

Water 800 ml
Sodium Sulfate 100 g
Sodium Carbonate 50 g
Formalin (37%) 10 ml

Water to 1 L

Use for 1 minute at 85 deg F then wash for 1 min at 85 deg F.

Soft films can be processed from 68 deg to 100 F with this, but the higher temperatures may require up to 5 mins to fully harden. Don't forget to wash after hardening.

PE

UnQuote----------------------------------

 

[Jeremy Saint-Peyre]

Hello RauschenOderKorn

I'm just having a look at what you said, sorry for the late reply and thanks for the time you take to poke around for me !

I'll try with a pre hardening bath next time, i have chrome alun at home, so i'll go with the Agfa 405 i guess. Is Sodiumsulfate absolutly necessary ? Is it one shot ?

Thanks again,

Jeremy