Ferricyanide bleach problem: white dots...

[Photopathe]

Hi!
I have this problem at the moment that when using the technique of overexposing under the enlarger and then bleaching with Potassium ferricyanide + P. bromide bleach for increased contrast and grain I get these white over-bleached spots. Anyone knows the source of the problem? I reuse my bleach to some extent. It didn't cause any problems so far, could that be the reason? I put the bleach back into a brown glass bottle. I try not to exaggerate on extending it's use. The spots appear while in the bleach bath.
Thanks in advance !

 

[Photopathe]

I just noticed that the back of the print looks like this even when I do a very light bleach and the white spots are not showing on the emulsion. There are black dots all over the back of the print.
The fixer (Legacy pro neutral rapid fixer) is very fresh. Could it be that I didn't rinse for long enough between fixing and bleaching?

 

[GregY]

P are your prints completely washed before you bleach them? I honestly don't know the cause of your spots... but I never reuse potassium ferricyanide. It has a very short life once mixed with water. I've only occasionally treated an entire print to bleaching but I often do selectively bleach. If you haven't already, I'd read Bruce Barnbaum's approach to selective bleaching. Also anything you can find by Jay Dusard, whose nickname is Captain Ferricyanide. Both are masters of selective bleaching. There's likely a section on the process in Beyond Monochrome.

I just noticed that the back of the print looks like this even when I do a very light bleach and the white spots are not showing on the emulsion. There are black dots all over the back of the print.
The fixer (Legacy pro neutral rapid fixer) is very fresh. Could it be that I didn't rinse for long enough between fixing and bleaching?

P, I always completely & fully wash my prints before bleaching. More often i even dry them (& then re-soak them before bleaching....because i want to decide what to bleach and a wet print doesn't give the most accurate tonal representation.

 

[koraks]

I never reuse potassium ferricyanide. It has a very short life once mixed with water.

Farmer's Reducer (ferricyanide + thiosulfate) does indeed have a short shelf life, but a solution of just ferricyanide or ferrycanide with e.g. bromide is very stable and will last for years unless contaminated.

The problem presented (i.e. the white spots on the actual image) is usually inherent to the structure of the paper. You'll get similar results when trying to lith print with this paper, or some form of peppercorn effect. It's due to slight variations in the actual emulsion or its interaction with the paper base and the baryta coating. Try a different paper - sometimes even different production batches of the exact same brand and type of paper will behave differently in situations like these where you stray far from the beaten path.

P, I always completely & fully wash my prints before bleaching.

This is important; any remnants of thiosulfate in e.g. the paper base will locally form Farmer's reducer, which tends to work a lot faster (and is irreversible) than a ferricyanide bleach. Especially baryta papers need to be washed quite thoroughly before ferricyanide bleach treatment.

 

[pentaxuser]

So, Photopathe, to advance this problem and hopefully get us closer to solving your problem, whose paper is this and how old is it?

Thanks

pentaxuser

 

[Photopathe]

Thanks!
I am in the darkroom again today. I am extending my washing time significantly to see if it makes a difference. Will report back.
The paper is mine. Ilford Classic mat bought last month from a batch produced in January 2023. Fresh Fomatone 132 produced the same effect yesterday.
BTW the bleach I use is the same rehalogenating bleach I use for my sepia (thiocarbamide) toning. So it is P. ferricyanide + P. bromide without fixer and it does have good keeping properties.

 

[pentaxuser]

Thanks so I'll venture it has nothing to do with your paper. On the other hand if your bleach is made up as it should be and it would seem so then I am at a loss to know what has caused this.

The way you phrased your problem in #1 may suggest that you have used this technique in the past with success. This may be a misinterpretation on my part and it may be that what appears to be a bleach redevelopment process is a new one for you

Unfortunately I could see nothing in Tim Rudman's book on printing which covers bleaching and redevelopment which warns of the problem you are experiencing

pentaxuser

 

[Photopathe]

Thanks Pentaxuser! You are right in your assumption: I used the technique with success in the past. I also have Tim Rudman's book and I checked before I wrote but then again I could have overlooked. I could not do everything I wanted today so I will report again but it does seem like extended washing time solved the problem. I was washing about 20 minutes running tepid water and today I did 45 minutes. I know 20 minutes is short but I had luck with that so far. When I tested in the margin of the print it always seemed to be ok...
Here is today's work, a 20x20" print. Beside is a 4x5" version with selective sepia+gold toning. I intend to apply to the larger print next time.
Thanks again!

 

[MattKing]

whose paper is this

The paper is mine.

Just smiling here at the vagaries of the English language.
In England, it seems not to be unusual to use "whose paper is this?" when one wants to know the answer to the question: "what brand of paper is it?"
In other parts of the world, pentaxuser's question means a question about ownership.
And it was duly answered that way by Photopathe.
All I can say is that I'm glad pentaxuser wasn't asking about pencil erasers

 

[Xylo]

Not all paper bases absorb chemistry in the exact same way. And washing temperatures probably have an effect on how fast the fixer leaches out of the paper.

 

[pentaxuser]

All I can say is that I'm glad pentaxuser wasn't asking about pencil erasers

You mean rubbers? I once knew an American in Aberdeen many years ago and he joined some friends and I for a coffee. We had a local shop called "the Rubber Shop" that sold great toys, puzzles and models. One of my local friends said that he had been to its third floor checking for any new items and the American asked with incredulity: "Gee, you have a rubber shop with three floors? It took us about an hour to stop laughing

pentaxuser