BW reversal: mix of negatives and positives on same roll

[pkr1979]

Hi all,

So Ive been developing Ferrania Orto in PQ 1+5 (with thiocyanate), dichromate bleach, clearing, iron out and fixing (washing between steps). Today I tried swapping the PQ with MCC at 1+2 (with thiocyanate) and ended with a weird mix of positive and negative images. I did check the roll after the clearing and it looked fine to my eye, so I doubt its the bleach. There is a chance I mixed the Iron Out in regular tap water instead of distilled battery water. So Im thinking its either that or the MCC. But as everything seemed fine after clearing the chance of the problem being the MCC also seems less likely.

Anyone got any ideas?

Cheers
Peter

 

[pkr1979]

I could also mention that there are more negatives at the center, and positives at the outer part of the reel (Paterson). I mixed the Iron Out in the water just before use (I still cant say if it is tap water or not).

 

[koraks]

Any chance of seeing some examples?

Partial negative suggests the bleach didn't go to completion. Did you use fresh dichromate bleach? Note that an acidified dichromate bleach isn't stable; it'll last up to a couple of days, but it'll die gradually.

 

[pkr1979]

Fresh dicromate bleach. Same recipe as always. Never had any problems. Examples may come.

 

[Donald Qualls]

Bad Iron Out wouldn't cause negative frames, it would cause thin positives, assuming the bleach step worked. But if the bleach didn't work, you should have gotten fully black frames, or positive with a very high Dmin (if you used light exposure reversal, you'd get Sabbatier effect). What it is I'm not sure, but I'm pretty confident what it's not.

 

[pkr1979]

Some of them might be a bit Sabbatier effect-like (they are stil hanging to dry). They are not reesxposed by light though - as you probably already knew - as I was using IronOut.

 

[pkr1979]

Is there any chance its caused by the first developer?

 

[Donald Qualls]

Not unless there was undeveloped halide in places that were supposed to be clear -- and even then, fully fog/developing the halide should have led to either full black or high Dmin positive images.

Now, a silver image negative or positive can appear to reverse with the right combination of front lighting and a black background -- like viewing an ambrotype mounted on black velvet, for instance. You might find, once fully dry, that the "negative" frames are actually normal positives like the rest of the film...

 

[relistan]

To me, it seems most likely to be a combination of two failures:

1. Incomplete bleaching
2. Either the first developer was partly exhausted, or the Iron Out was not mixed or circulated in the tank well enough

Both could also indicate that it was not spooled properly, but presumably you unspooled it so I assume that was not the case.

 

[pkr1979]

Im not sure how helpful these mobile scans are but they should help some. The first one is of a piano, and the beginning and the ende of the film. The next are to frames next to each other on the roll, one negative and the other 'positive'. I think its strange that two so close frames are so different. The last one is kind of a positives I guess.

I cant understand that this is the bleach as Ive been using the same stuff mixed up the same way for ages. Any clues?

 

[loccdor]

Looks like the Sabbatier effect I was getting on a C-41 reversal process of Aerocolor I recently tried... I notice your underexposed image of the kid is negative while your picture of him with more exposure is positive - that is the threshold effect I was seeing as well, although I saw it in reverse, with the brightest parts of my image turning negative. However I don't know why it's happening here.

 

[koraks]

I'm not sure either what's going on here; a couple of possibilities come to mind which would have to be eliminated one by one:
1: Failure of the fogging exposure (chemical in nature in this case). This can be verified by using an optical fogging exposure instead and see if that helps.
2: Failure of the bleach, although I'd frankly not expect this to be the root cause
3: Failure of the fogged silver halides to successfully develop in the reversal developer for whatever reason.

It's been suggested before in similar instances, although permanganate instead of dichromate bleach, by @Alessandro Serrao that metabisulfite is required in the bleach clearing bath (e.g. here: https://www.photrio.com/forum/threa...-process-with-photo-paper.213019/post-2886497) IDK, might be worth a shot in case #3 turns out to be part of the problem. I couldn't say, really; I use dichromate bleach in a different application (intensification) and given sufficient re-exposure, all silver always successfully redevelops.

 

[pkr1979]

Ive been using sulfite for clearing for a long time without any problems. It is also my impression that most people using dichromate use that without any issues.

 

[dokko]

I used dichromate bleach after sulfite clearing bath for many years for reversal super8 processing (as per the old Kodak instructions), never had any issues and the bleach was stable for weeks (if not months).

now I'm using permanganate bleach with sulfite clear (per the modern Kodak instructions) and have to be much more precise in the procedure not to get solarisation issues.