[Frameworks] alternative processes to c-41 & e-6 + onions as fixer?

[Scott Dorsey]

> 
> 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