Fogged Paper - Preliminary Experiment

[newcan1]

I have a lot of fogged RC VC paper. I developed a sheet recently, and it was about 18% grey. I wondered if it could be salvaged.

Remembering an earlier thread here, I decided to develop some sheets under an appropriate safelight, wash then bleach in a ferricyanide/bromide bleach, then wash and try to re-use for printing (all under safelight). The result was disappointing: The results were thin, paper very slow, and very low contrast.

Then I decided to try bleaching without developing first. The results are interesting. At Grade 1, results are similar to those with other papers, except exposure is way longer. Change the filter to higher grades, and paper is much faster. Little to no base fog. I think a good deal of variable contrast control is lost, however. I need to experiment more and with more negatives, but it seems this now makes maybe a useable Grade 1 and 2 paper, but perhaps not higher contrast.

I bleached for 30 sec and washed for 1.5 min and blotted, then used the still drying paper to print with. So it adds a couple of minutes a sheet to darkroom printing times. I only did test prints today; I'll try something more critical later in the week.

 

[bernard_L]

Very interesting. In "theory" (fwiw) ferricyanide/bromide should have no action on unexposed, undeveloped emulsion. Possibly it resets some sensitized sites?
Would be nice if a knowledgeable chemist would chime in and explain.

 

[Ian Grant]

Very interesting. In "theory" (fwiw) ferricyanide/bromide should have no action on unexposed, undeveloped emulsion. Possibly it resets some sensitized sites?
Would be nice if a knowledgeable chemist would chime in and explain.

In the presence of excess bromide the latent image silver can be returned to the halide state, it doesn't need developing first, see the Herschel effect. The Ferricyanide in the bleach will do this very easily.

Ian

 

[pdeeh]

Apologies if I have got hold of completely the wrong end of the stick, but I'll suggest this anyway.

Am I correct in understanding that the mechanism of age-fogging in emulsions is mostly due to a "natural" process whereby development centres (i.e. silver specks) form in a random and widespread way in the emulsion as it ages?

in which case, non-rehal bleaching away a proportion of those centres before exposure and development would tend to decrease fog somewhat. Although on the you-can't-get-something-for-nothing principle the trade off is presumably loss in contrast &/or sensitivity through some other mechanism.

(I think SLIMT is supposed to work in an analogous way with exposed materials for contrast control, isn't it?)

 

[Ian Grant]

Older texts recommenced bathing a weak ferricyanide/bromide bleach for restoring fogged papers, followed by washing and drying. You need to re-halogenate, there would be no benefit from removing the fogged silver as you would in effect end up with a reversal -a lighter area where the fog was removed on re-exposure & development.

Ian

 

[Athiril]

You can also try using excessive restrainer (relative to lightly fogged paper) in the developer.

 

[pdeeh]

I've used benzotriazole with very old Kodak Bromide paper with almost miraculous results.

 

[Xmas]

I've used benzotriazole with very old Kodak Bromide paper with almost miraculous results.

Some papers will tend to tone to warm with the addition of Potassium Bromide and more dilute developer they willl also be less foggy as well. Lots of test strips needed...

 

[pdeeh]

Well, yes.
But benzotriazole is not KBr and will tend to cool paper.

 

[Xmas]

Well, yes.
But benzotriazole is not KBr and will tend to cool paper.

Confirm both your phrases but if you want to reduce fog and maybe go warmer ...

 

[newcan1]

I had previously used benzotriazole in various concentrations with this paper, and could not achieve acceptable results. The one thing that remains to seen is whether or not the paper is still variable contrast. I think somewhat, but I will do further testing.

Now I wonder how this technique will work with film. I have some badly age-fogged Ilford HP3....I have owned it since I was a teenager (I'm now 55)..it has never been cold stored and while it will record an image, the base fog is very dense.

Finally...I wonder if it would work with RA4 paper, although the process would remove the soluble dyes in the paper. I may try this next time I do color printing.