Re: fogging developer

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From: Jack Fulton (jfulton@itsa.ucsf.edu)
Date: 07/21/02-09:27:54 PM Z


This is a reversal formula . . the "deadly" part is that it's made of a tin
compound (stannous chloride). It is a rather simple thing to reverse film
w/light after a light stop bath. You can use ANY light to do this:
fluorescent, tungsten, day . . . they all work.

Also, if you don't use the reversal bath for a while, it will develop a
rather ucky gelatinous sludge inside the bottle. If it has sat around for a
while, I'd pour it out first to see if the uckiness has occurred.

> An old booklet I have here gives a chemical reversal bath for reversal
> colour film/prints, instead of re-exposing to light. I think I've used it
> and that it worked, but so long ago that I don't remember the details.
> Formula is:
>
> Propionic acid 15 mL
> Stannous chloride 2 g
> Sodium hydroxide 5 g
> Water to make 1 L
>
> The instructions are:
>
> Instead of re-exposing colour reversal films to light, the above may be used
> after the first developer in place of the first stop bath. Take care to
> avoid contact with this bath and wash hands and all containers thoroughly.
>
> Rinse the film for half a minute after the first developer. Do not use the
> stop bath. Treat the film in the reversal bath for 2 minutes at 38 deg. C
> and then wash for 2 minutes in running water before continuing the rest of
> the process.
>
> This will probably do the trick (maybe extend the time a little at the lower
> temperatures used in B&W work?) Didn't the old E-4 process use something
> else to do the same job - tetrahydrofuran or something like that, but I seem
> to remember it was highly toxic. And presumably still is.
> Liam
 
>
> I wonder whether anyone out there knows of a readily available agent that
> will develop silver halide regardless of whether it has been exposed (a
> useful way to avoid the need for reexposure in reversal development). Kodak
> has used Sodium Dithionite (95% Sodium Hydrosulfite), about which I know
> nothing nor where one might get it, and a Barbitol compound, but this is
> hard to get, being a barbituate and hence a controlled substance (although
> there is no doubt a source I am not familiar with). A low-tech solution
> would be preferable. What works as a reducing agent for AgH without needing
> exposure?


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