Any possible way to re-expose?

YJL · Nov 3, 2020

I know only beach process with potassium ferricyanide, which I can fix or re-develop. Then I was wondering if there are any possible way to re-expose exposed bw print?

For instance, after I printed one bw print then completely bleach and fix it(ideally to make blank paper again), then what process would make the paper photosensitive again? Only adding new layer of emulsion would be only way?

Donald Qualls · Nov 3, 2020

In theory, it should be possible to soak the emulsion in a solution of halide salts (some combination of chlorides, bromides and iodides), let it dry, then apply silver nitrate solution (in a way that doesn't wash the salts out), which would form silver halides in place in the gelatin coating. This would most likely give a printing-out emulsion similar to salt print, but bound in the gelatin rather than applied directly to the surface of paper.

YJL · Nov 3, 2020

Thanks for the quick answer! I appreciate it, and amazed by knowledge!
That sounds really complex and almost impossible for me. If you know any cases done through this process?

Donald Qualls said:
In theory, it should be possible to soak the emulsion in a solution of halide salts (some combination of chlorides, bromides and iodides), let it dry, then apply silver nitrate solution (in a way that doesn't wash the salts out), which would form silver halides in place in the gelatin coating. This would most likely give a printing-out emulsion similar to salt print, but bound in the gelatin rather than applied directly to the surface of paper.

Donald Qualls · Nov 3, 2020

It's really not difficult. You'll need potassium bromide, potassium iodide (easy to get and cheap) and silver nitrate (less easy and much less cheap, but you don't need much). Look up the process of making "salt prints" or "salted paper prints" -- it was one of the methods of making prints from collodion plates in the 1860s.

For this purpose, you'd soak the fixed-out photo paper in the solution of salts (about 2% solution by weight, as I recall), let it dry, then briefly dip the emulsion side in the silver nitrate solution (I don't recall for sure, but likely 1% by weight) for just long enough to wet the surface well, or alternately spread the silver nitrate solution on the print with a soft brush or a glass rod. Let the paper dry in the dark or under dim incandescent light; it'll be sensitive only to ultraviolet light, so if you avoid fluorescent and LED lights you'll be fine even in subdued room light. Once dry, expose as a contact print by direct sunlight or under a UV lamp until the print is a little darker than you want your final result, and fix in weak plain hypo fixer. The image will be brown on white.

YJL · Nov 3, 2020

Thank you for your answer. I definitely need to follow your instruction after I get all the materials.(I am based in EU and it ssems silver nitrate is a bit hard to get it, even from the photo suppliers)

What you explained the process salt prints in the end?(I just caught 'salt' and 'brown image') I only saw and read about it but haven't tried it myself yet. If so, back to the beginning of my question, could I be able to make "normal(modern version of)" black and white printable surface as well?(to expose by enlarger and to control contrast)

Donald Qualls said:
It's really not difficult. You'll need potassium bromide, potassium iodide (easy to get and cheap) and silver nitrate (less easy and much less cheap, but you don't need much). Look up the process of making "salt prints" or "salted paper prints" -- it was one of the methods of making prints from collodion plates in the 1860s.

For this purpose, you'd soak the fixed-out photo paper in the solution of salts (about 2% solution by weight, as I recall), let it dry, then briefly dip the emulsion side in the silver nitrate solution (I don't recall for sure, but likely 1% by weight) for just long enough to wet the surface well, or alternately spread the silver nitrate solution on the print with a soft brush or a glass rod. Let the paper dry in the dark or under dim incandescent light; it'll be sensitive only to ultraviolet light, so if you avoid fluorescent and LED lights you'll be fine even in subdued room light. Once dry, expose as a contact print by direct sunlight or under a UV lamp until the print is a little darker than you want your final result, and fix in weak plain hypo fixer. The image will be brown on white.

Donald Qualls · Nov 3, 2020

It's a much more advanced process to make a developing-out emulsion like the one that was on the paper to begin with -- even leaving aside the process required to make a multi-grade paper (blue-sensitive and green-sensitive emulsions mixed together to produce varying contrast depending on the color of light used for exposure).

Also, I didn't mention, the simplest form of salt prints use ordinary table salt, sodium chloride -- and they work well.

In the end, fixed-out photo paper makes a good base for "alternative process" printing, but it's not really practical to restore or replace an emulsion that will work and look like the original.

RalphLambrecht · Nov 3, 2020

YJL said:
I know only beach process with potassium ferricyanide, which I can fix or re-develop. Then I was wondering if there are any possible way to re-expose exposed bw print?

For instance, after I printed one bw print then completely bleach and fix it(ideally to make blank paper again), then what process would make the paper photosensitive again? Only adding new layer of emulsion would be only way?

Yes, after you bleach and fix all sensitive silver is gone. The point he will have to apply new emulsion to make the paper photosensitive again

YJL · Nov 3, 2020

Dear Donald and Ralph,

Thank you for the clear answers. I very much appreciate it.

Any possible way to re-expose?

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