Is there a way to convert the AgBr contained in usual modern paper into AgCl, and thereby to prepare a pure silver chloride paper?

Thank you.

-- Andrey Vorobyov (AndreyVorobyov@hotbox.ru), May 17, 2002

Answers

Yes you can through the process of ion exchange. Supprisingly, a recently chlorinated swimming pool has an abundance of free Cl- ions just waiting to do something. Simply put a box or two of your favorite AgBr paper in the pool and the Cl- ions will replace the Br- ions in aboout 3-4 hours. Obviously you have to do this at night! You can speed the reaction somewhat with electrolysis if you have a spare 12 volt car battery. Don't use 120 volt house current for obvious reasons. The paper can be hanged to dry, but again, in the dark. I discovered this one night during a Corona induced state of enlightenment. Sometimes when I don't have time for this conversion process I go to the local photo store and buy a box of AgCl paper.

-- r (ricardospanks1@yahoo.com), May 17, 2002.

Ricardo, it sounds also very creative, but since I don't visit swimming pool and since photo stores in my city don't have chloride papers, I cannot take full advantage of your enlightening ideas.

-- Andrey Vorobyov (AndreyVorobyov@hotbox.ru), May 17, 2002.

I had a feeling you might have a problem at the swimming pool end. anyway, I really don't think what you're asking is possible. perhaps you can try some post processing toning to simulate a chloride paper. good luck.

-- r (ricardospanks1@yahoo.com), May 17, 2002.

The pure chloride papers (Velox, Azo, Athena, et al.) were all so slow they could only be used as contact papers.

-- Ed Buffaloe (edb@unblinkingeye.com), May 17, 2002.

As Ed points out, the silver halides vary in their sensitivity. Chloride is the slowest and iodide is the fastest. They also have somewhat differnet spectral sensitivites and colors. Silver chloride is considerably slower than silver bromide and silver chloride is principally sensitive in the blue and violet regions, while bromide is sensitive further into the visible spectrum. Both silver bromide and silver chloride have essentially the same crystal structure, although there is a difference in the size of the crystal lattice - the silver chloride is smaller, which I suspect is why silver chloride emulsions are easier to get warm/cool tones out of. The three halides of silver show a gradual deepening of colour - silver chloride is white, silver bromide is pale yellow and silver iodide is yellow. Why might these colours occur? One speculation I have encountered for this is that the compounds become less ionic on moving from the chloride to the iodide. Thus the charge transfer band would move from the ultraviolet and start to encroach into the blue giving the compound a yellow appearance.

All of which is a very loooong way to say that the emulsions do seem to provide very different aesthetic qualities. Anywho, if you want a pure silver chloride emulsion, I would suggest you just buy some Azo.

Cheers, DJ

-- N Dhananjay (dhananjay-nayakankuppam@uiowa.edu), May 17, 2002.

You might be able to do it by a bleach process. Expose a sheet of paper to white light and develop it to maximum black. Bleach it in ferricyanide-chloride bleach, like that used for sepia toning except sodium chloride (table salt should do)is used in place of potassium bromide. Do this under the safelight,of course. Dry the paper and try to print on it. It may do for contact prints. I haven't tried it.

-- Patrick A. Gainer (pgainer@rtol.net), May 22, 2002.

Thank you, Patrick. There are some more questions, e.g. about sensitivity after exposure/development/rehalogenizing (even again with Br), but I think the best is to try.

DJ, thank you too: few days ago I have discovered your article about Azo toning at Michael & Paula site, and you're (partially) in charge of my interest in chloride papers ;)

-- Andrey Vorobyov (AndreyVorobyov@hotbox.ru), May 24, 2002.