Fogged Paper - Chemistry Question

[newcan1]

I have some fogged enlarging paper on which I have gotten good results by slightly over-exposing then bleaching back after development. However, the technique is a bit hit and miss.

I wonder if it would be possible to use a rehalogenating bleach to remove the fog prior to exposure. My sense - but please correct me if I am wrong - is that this might work if I first developed unexposed sheets, then bleached them, then washed and dried for use.

My question - other than to probe the above - is whether development would be necessary. What would happen if I simply bleached unexposed paper? Would this remove the fog?

Also, any other suggestions (other than "don't waste your time") would be greatly appreciated.

 

[Gerald C Koch]

Instead of bleaching a print try this. Use an antifoggant such as 10% potassium bromide solution or 1% benzotriazole solution added to the developer. Start with 2.5 ml/l of either solution and increase the amount by 2.5 ml until the fog is under control. If you have to add more than 25 ml to reduce the fog then it's best to discard the paper.

 

[David Lyga]

Yes, even use more of the reducer if the paper is heavily fogged, i.e., even more that 25ml per liter. Sometimes that actually works better. The Ideal development time is found by doing a coin test: when the coin area has only medium density, that is enough development. More will make it impossible to reduce that coin area without doing serious damage to the darker tones.

The reducer will 'bring back' that coin area to pristine white and, hopefully, not do much damage to the blacks and darker tones. That's why you must give an exposure such that the print, after fix, is darker than you normally would want it to be. It does take experience to do this correctly, as we are used to not having to worry much about overdevelopment with paper whose whites remain white. - David Lyga

 

[yulia_s_rey]

Instead of bleaching a print try this. Use an antifoggant such as 10% potassium bromide solution or 1% benzotriazole solution added to the developer. Start with 2.5 ml/l of either solution and increase the amount by 2.5 ml until the fog is under control. If you have to add more than 25 ml to reduce the fog then it's best to discard the paper.

newcan1, go with Gerald's recommendation. This is similar to my previous experiments on "recycling old film." I'v tried it on numerous papers and films, while the process does work it has many more cons than it has pros. I've tried numerous bleaches and dye baths and in conclusion, unless you want to work with an incredibly slow speed (highest I ever got was 1.6) and a blue sensitive stock. In my opinion it is not worth the hassle.

 

[Ginette]

I have some fogged enlarging paper on which I have gotten good results by slightly over-exposing then bleaching back after development. However, the technique is a bit hit and miss.

I wonder if it would be possible to use a rehalogenating bleach to remove the fog prior to exposure. My sense - but please correct me if I am wrong - is that this might work if I first developed unexposed sheets, then bleached them, then washed and dried for use.

My question - other than to probe the above - is whether development would be necessary. What would happen if I simply bleached unexposed paper? Would this remove the fog?

Also, any other suggestions (other than "don't waste your time") would be greatly appreciated.

Is it RC or FB paper?
Theses fogged papers can be great for paper negatives. If you don't have a 8x10 camera, you can use or built a pinhole camera in that size.

 

[pstake]

Use the paper for Lith.


Sent from my iPhone using Tapatalk

 

[newcan1]

I have tried benzotriazole, but even with large quantities some fog remains. I haven't tried potassium bromide. But I would have thought that using a rehalogenating bleach would not have affected the properties of the paper much... only to the extent of the fogged component of the emulsion. If 90% of the emulsion were still intact/unfogged, would that 90% not still perform as originally? The rehalogenated 10% may be blue sensitive and slow, but so what?

 

[yulia_s_rey]

newcan1 I see what you mean. It does make sense, but I think somehow it won't work, call it a "gut feeling" by applying how the reversal process works. I'd say there are two options a) an experiment or b) someone who can explain how silver atoms that don't have specks (un-fogged) versus those that do will react in the bleach. Again, notice by my lack of lexicon in chemistry I wish I could expand on the latter.
Although emperically, I believe that the bleach affects both "specked" & "un-specked" (for lack of a better word Ag halides. In my thread about recycling fogged film it was pointed out that:

While the bleach may convert the silver to silver chloride, modern films are mostly silver bromide with some silver iodide.

First, ignore the chloride and insert Br/I. What I understand from this is to achieve what you are describing is only theoretically possible by knowing the exact composition of your film/paper and then doing a whole bunch of chemical equations to "make the perfect bleach" for that particular stock. The equations for those with experience are most likely a piece a cake, but what <i>isn't</i> is finding out the exact composition of your film/paper (& percentage of fogging too I suppose.) Now add to this the whole dye-sensitization variable. I hope I didn't confuse the matter and I'm sure those who do understand the exact process are rolling in aisles now because of my laymen's explanation/deduction, but from what I gathered from my notes and experiments this is the conclusion I have come to.

 

[newcan1]

I would most likely use a bleach of Potassium Ferricyanide plus Potassium Bromide. My understanding -- which may be incorrect -- is that the bleach would only affect metallic silver, so it may be that the paper may first have to be developed.

 

[Doremus Scudder]

I would be interested in learning what effect pre-exposure bleaching would have on fogged paper. Even though the fog is likely not reduced metallic silver, it is still a latent image of sorts. It is well-known that SLIMTs can have a marked effect on paper response. So, the paper need not be developed first for the bleach to have an effect.

A couple of scenarios present themselves: 1. a weak rehalogenating bleach before print exposure (meaning you would have to print wet). 2. a SLIMT treatment before developing but after print exposure.

It would likely take some experimentation. There is a good article on unblinking eye about SLIMTs for prints. Might be worth a try if you have lots of time.

Best,

Doremus

 

[yulia_s_rey]

newcan 1, I'd try both (undeveloped and developed) and a control. I'm interested in your outcome.