no worries newcan1. To answer your questions from above: a) a latent image within a silver halide emulsion is lost in re-halogenizing. b)only the oxidized metallic silver is converted back to a halide. c) the film will not retain the same speed nor sensitivity to color. (although I could be wrong on the last one in terms of color sensitivity.) I like to think of it as starting from scratch with the stock, essentially it is just recycling something that would've otherwise gone to waste. The key is to intentionally fog your paper/film under a lot of light and develop it well (to oxidise the Ag fully) and then bleach it. Then run your exposure/dev tests.
You can also expose the film to fumes of hydrochloric acid, or mix a little sulfuric acid + potassium permanganate + sodium chloride in a 'gassing tank' (tank reserved for the process), load it in, a spacer reel at bottom so film doesn't get wet, that's a dry process and works well too.
The other idea to do, is sleeve some film in plastic and leave it out in the sun for a week, to 'print-out', the grain will be much much finer. Gas bleach it back, ultra slow very fine grain film.
Interesting idea of that dry bleaching.
This is what PE wrote on the matter of rehalogenisation for re-using halide materials for first stage exposure:
Originally Posted by Photo Engineer
Out of curiousity. This is all a wild guess bases on the idea that the silver in the emulsion is AgCl after CuCl bleach.
You expose the hell out of it, develop to black, bleach it so I assume no dyes were left in the gelatin emulsion that make the film panchromatic.
Assuming, CuCl bleach turns the silver halide in the emulsion to AgCl. This is the same silver halide in salt print/albumen.
If so, it is probably more sensitive to UV than visible light. But, salt prints are much more sensitive to visible light than most of the other alternative processes.
If so I would expect a visible image on the film before developing, if it is AgCl in the emulsion. Even developing might not be necessary.
If anybody would enlighten me, Is it possible that silver halide is AgCl in the emulsion after CuCl bleach?
Logically it should be, in the presence of copper ions, the Br- can recombine with the Ag+ (ala transition lenses). But logically Chlorine should displace Bromine and Iodine in salts, and Bromine should displace Iodine if using a Bromide bleach.
Though, that's mostly assumption.
Also afaik, the simple act of washing doesn't remove spectral sensitisation (at least not all of it), haven't investigated bleaching though. Saw another user wash the antihalation out of some IR film, and the film maintained it's pan and IR sensitivitiy. Though I suppose it'd be dependant on how well fixed in place the sensitisation dyes are.
Originally Posted by Athiril
If the film is exposed to enough light to develop maximum black, and then developed in dektol 1+1, how much bromide would remain or would it even remain. Isn't bromide supposed to be removed during the development.
I agree, this is all based on assumptions, but sounds very plausible. Having an AgCl film is quite an interesting idea to me.
The adherence of spectral sensibilisator dyes differs between materials.
Not the least in dependance of the intented use of the emusion.
Why do you need to fully expose the film? I have some old HP3 that has a very dark fog, but I can get an image from it. Couldn't I develop some before using, bleach it, and presto - the fog would be gone? Wouldn't the rest of the emulsion (ie minus he fog) still work at its "original" (ie pre-treatment) speed? I wouldn't get any better image than before, but I wouldn't have to print through thick fog.
Also, would ferricyanide bleach work for this? Or EDTA bleach?
From what I gather, it is essential to fully expose the film/paper in order to "recycle" it. I would think if your HP3 is partially fogged and you develop it, you won't achieve a "max black" before re-halogenization, otherwise the bleach will only act on the grains which are partially oxidized and you'll still have the same problem (only in reverse). In no way would it be possible to bring the film/paper back to its former glory. It is, as PE is quoted beforehand, "reverts[ed] to a simple blue sensitive emulsion with low speed, usually in the ISO 3 - 40 range if you are lucky." which makes sense. Initially, I wasn't sure about the color sensitivity. But now after reading the previous posts and a bit of research it makes sense as well as why it would not retain its original spectral sensitivity.
Not sure about the other bleaches as I have very limited experience with them as I usually use a Blix provided in kits.
Well I find this all very interesting. I have tons of waste imagesetter output; now I can scavenge all the pieces that are fully black, cut them into 6.5x9 cm rectangles, and bleach them to play with in my old Zeiss Ikon Maximar A. I could probably rustle up 100 or more cut sheets like this from the scrap output I have.
The film is imagesetter film, it's been developed and fixed, but that should not matter, should it? The imagesetter produces high contrast graphic output, so black is very black.