Hi all, For what this is worth as anecdotal data : The onions seemed to work as a fix, and enabled me to have a reasonably clear negative to print off (this is all relative, of course) immediately after., However, after a year the negative lost clarity with a yellowish fog not unlike an unfixed film. The images were still visible, but it looked unlikely that it would be possible to print a decent copy. I put a short length in a standard Agefix bath and it fixed it perfectly. The seawater test I did either had no effect on the film or the little effect it did have was unstable, even after two days. The chemical mix is obviously variable for seawater (this was from the North Sea, off the coast of Northumberland). I did a workshop in Nottingham, England with some of my students and they built up a decent set of tests for coffee development, getting the time down to 10 minutes (coffee/washing soda half and half at 30°-27°C using Kodak 7222), with good contrast. This seems to be too high a temperature, beyond the range authorised by Kodak, but the film did not buckle, even in the 40°C test. Since wine is abundant where I teach (Tours, in France), we will be going with wine for next years films, but as onions as a long term fixing agent don't seem to work, we will look at other sources. As you can see, this is essentially rumour based research. The guys at Mire in Nantes, France, have a greater knowledge of chemistry and its history, and have done some solid work on this. Good luck, David
On Mon, Jul 9, 2012 at 8:23 PM, Scott Dorsey <[email protected]> wrote: > > > > Hello all,=0A=0AI've been experimenting with various alternative > formulas f= > > or black and white developing that involve non-toxic household chemistry > bu= > > t I am curious if anyone has done so for color film?=A0 =0A=0A=0AAlso, > why = > > and how do onions work as a fixer?=A0 How do you prepare them to do so? > > Okay, B&W process is easy. Single layer of emulsion, it's got silver > halide > compounds in it. Light strikes them, knocks electrons off, they get > charged. > > You put it in a developing agent which converts the exposed crystals to > metallic silver. Then you put it in a fixing agent which removes all the > free halides. > > There are millions of developing agents out there, and a lot of them are > mentioned in Mees' "Theory of the Photographic Process." There are several > different ways that they work. Most of them like to work in alkali > solutions, > some (like pyro) like acid solutions. > > Among the things that kind of work for development are coffee. Since > catechin > is a weak developer, a strong cup of tea might also work. You can look > through > Mees and see some of the various possibilities. > > For fixing, just about any reducing agent will kind of work. Thiosulfate > is nice because it combines the all the various halide compounds rapidly > and well and the end products are very soluble. Sodium cyanide works even > better, but it's nasty stuff. > > My inclination is not to try using anything but standard thiosulfate fixers > unless you really know what the end products of the reaction are and how > soluble they are. I know onion and table salt seem to work, but you can't > necessarily know what they're leaving behind in the emulsion and you won't > know what they have left for a decade or two, possibly. > > And no, the Kodak Hypo-Check kit is basically a test for residual > thiosulfate > ions in the emulsion, it won't detect whatever is left over from onion > fixing. > > > I know an extreme salt solution (extreme as in you put in so much salt > the = > > water can't take it anymore) will work too but it takes a long time (2 > days= > > I heard). How long do onions take? > > Same as with any other fixer.... twice as long as it takes for the film to > clear. The one time I tried it, it was all afternoon. > > >=A0 Isn't the real danger from fixer the= > > metallic silver that needs to be properly disposed of? > > Yes. Except that it does not need to be disposed of, it needs to be sold > because silver is increasingly worth money. Don't waste it, ask your local > print shop who does hypo disposal for them! > > >=0A=0AFinally, has a= > > nyone come up with a good substitute for r-9 or r-10 bleach in the bw > rever= > > sal > process.=0A=0AThanks=0AKathryn=0A=0A=0A=0A_____________________________= > > The reversal bleach needs to be something that will dissolve metallic > silver > without affecting the unexposed halides. > > R-9 is the traditional sodium ferricyanide bleach, it works very well and > it's not really all that toxic unless it is combined with an acid. > > R-10 is a mix of potassium permanganate and sulfuric acid that produces > potassium persulfate in solution which is what does the actual job. > > I don't know of any easy natural sources for any ferricyanide or persulfate > compounds, but I know that sodium ferricyanide was known in the 18th > century > and is used in making prussian blue dye. My suspicion is that to do a > proper bleaching job you will need something from one of those two chemical > families. > > ANYWAY.... > > to answer your original question, Kodak process color films all have > most of the complicated stuff built into the film, not into the processing. > There are three individual layers of B&W emulsions, each sensitized for a > given range of light colors, and each with a dye material in the emulsion > itself. (Yes, I am oversimplifying this in the case of the yellow layer > but I've already gone on too long). > > The first step is a conventional developer that generates a conventional > silver B&W image on each of those layers. You can use whatever developer > you want, including coffee or Acufine or whatever gives you the look you > want. > > The second step is where all the fancy stuff goes. The color developing > agent connects those dyes up to the metallic silver in each of those > emulsions > and since the dyes are in the layers when the film is made, each layer gets > connected to dye of the proper color. This is the fancy stuff, and there > is no substitute for the color developing agents. I believe they can both > be ordered in small quantities from Photographer's Formulary. If you try > and order CD-3 from Kodak their minimum order is a barrel. > > Then it's just a matter (for negative film) of washing out the unneeded > dyes, bleaching out the silver image, and cleaning up any residual > undeveloped > halides. You can, in fact, leave out the bleach step and leave the silver > image and the color image behind together, which gets you a more contrasty > image with less saturation. This used to be a standard trick for press > photographers working in low light. > > Aside from the color developing agent and the bleaching, the color process > is very much the same as the B&W process. This whole thing is ingenious > as hell especially when you compare it with Kodachrome or Agfachrome. > --scott > _______________________________________________ > FrameWorks mailing list > [email protected] > https://mailman-mail5.webfaction.com/listinfo/frameworks >
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