[alt-photo] Re: Chemical Development for Printing Out Processes

[Francesco Fragomeni]

This is great information. Thaks Ryuji!

-Francesco

On Sat, Sep 8, 2012 at 10:27 AM, Ryuji Suzuki <rs at silvergrain.org> wrote:

> In order for the developer to discriminate exposed AgX crystals from
> unexposed ones, the crystals in the emulsion must be exceptionally "clean"
> meaning free of defects that act as fog center. It goes without saying that
> the crystals must not be exposed to any light that can create latent image
> center, as well. These are very important factors when making silver
> gelatin emulsions for developing process. Printing out process emulsions
> are full of crystalline defects and when electrons are injected through the
> developer they are going to develop with ease, with or without intense
> exposure required to produce print out images. The result is dense fog.
>
> Old physical developers can act in somewhat different way, by adjusting
> the reduction potential of the developer to a level that's barely enough to
> reduce silver ion from the solution on bulk metallic silver surface (c.f.
> silver intensifier). That's why I suggested to experiment with developer
> exhausted by actual developed out print processing, that is, lower
> developer concentration, lower pH, and some reducible silver complex ion in
> the solution. Even then, it will be a somewhat tricky task because the
> window of reduction potential that does not cause massive fog but still
> augment the image development will be fairly narrow.
>
>
> --
> Ryuji Suzuki
> "No matter how much you study or improve vacuum tubes, you will not arrive
> at a
> transistor." (Leo Esaki)
>
>
> Richard Knoppow wrote:
>
>>
>> ----- Original Message ----- From: "Francesco Fragomeni" <
>> fdfragomeni at gmail.com>
>> To: "The alternative photographic processes mailing list"
>> <alt-photo-process-list at lists.**altphotolist.org<alt-photo-process-list at lists.altphotolist.org>
>> >
>> Sent: Friday, September 07, 2012 9:12 PM
>> Subject: [alt-photo] Re: Chemical Development for Printing Out Processes
>>
>>
>>  Ryuji,
>>>
>>> Thanks for the reply. So your thought is that the higher ph and potency
>>> of
>>> a modern developer (unused) would cause fog in a POP emulsion.
>>> Interesting
>>> and I hadn't considered that but it makes sense as a possibility.
>>>
>>> By the way, I'm not particularly interested in recreating the results of
>>> historic literature or figuring out what works best for the purpose,
>>> hence
>>> the question about using modern developers with POP emulsions. Its a
>>> mismatch intentionally. My interest is simply in seeing what the results
>>> might be simply for the sake of curiosity.
>>>
>>> Has anyone actually tried this who can confirm Ryuji's fog hypothesis?
>>> Or,
>>> do any of you Albumen practitioners have an extra test strip and some
>>> Amidol or other print developer sitting around that you can test with
>>> next
>>> time you print? I'm still setting up my space otherwise I'd try it.
>>>
>>> Thanks for contributing Ryuji and anyone else who chimes in.
>>>
>>> -Francesco
>>>
>>>  Perhaps Ryuji can explain the differences in developing out and
>> printing out
>> coatings. I have only a little understanding of this but I believe POP
>> coatings
>> do not allow the developer to discriminate between exposed and unexposed
>> silver
>> crystals, at least not very much.
>> The usual process for POP whether gelatin-silver or salt or albumin is to
>> allow
>> light generated silver to form and then intensify it using a suitable
>> toner. The
>> unused silver halide is removed either co-incident with the toning or
>> afterward.
>> Some toners are not suitable because they will tone all the silver
>> regardless of
>> whether it in metallic form or not. Here again, I am not sure I
>> understand why a
>> gold toner, for instance, will tone an unfixed POP print while something
>> like a
>> sulfiding toner will simply turn the whole thing to silver sulfide. Fixing
>> before toning tends to remove the image silver along with the non-metalic
>> silver, perhaps because it is so fine.
>>
>>
>> --
>> Richard Knoppow
>> Los Angeles
>> WB6KBL
>> dickburk at ix.netcom.com
>>
>>
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