From: Carl Weese (cweese@earthlink.net)
Date: 06/24/01-01:40:31 PM Z
Ken,
The important point--what makes pyro useful--is that the stain is
proportional to the silver. It's never occured to me that the physical site
of the stain would be anywhere other than the gelatin. How, and to what
effect, would you stain miniscule particles of suspended silver?
The functional aspect is that the stain is at its greatest where the silver
is most dense, and vice versa. This means that for a receiver sheet that
"sees" the stain as 'low contrast data' (variable contrast silver paper) it
has the useful effect of printing highlights softer and shadows harder. For
a receiver sheet that "sees" the stain as quite opaque (UV-sensitive
processes like Pt/Pd) it has the useful effect of printing the same negative
as contrasty enough for the process. So the proportional green/yellow
stain--presumably in the gelatin--is directly (proportionally, to be more
precise) related to the silver image, and very usefully so. Another way to
think of it is to consider the stain a wonderfully useful set of contrast
control masks, automatically generated as the film is developed.
---Carl
--
web site with picture galleries
and workshop information at:
http://home.earthlink.net/~cweese/
----------
>From: ken watson <watsok@frii.com>
>To: alt-photo-process-l@sask.usask.ca
>Subject: RE: Pyro and staining
>Date: Sun, Jun 24, 2001, 3:17 PM
>
> Mike,
>
> From using Pyro I agree generally with what you are saying . But then the
> question with the gelatin folks is why do they want the stain if it is NOT
> associated with the image / silver in the emulsion?. This was my point of
> asking the question as I know a lot of folks who do use Pyro are on this
> list. I seem to remember there was some discussion about IF the stain was
> associated with the image and I think the fact that Pyro stain is not
> present in Collodion is a data point that says Pyro is only staining the
> gelatin and really has no correlation with the image.
> I would like to hear counter discussion as to why this is not good info or
> there is something I am overlooking.
>
> ..-----Original Message-----
> ..From: MICHAEL STEINLE [mailto:mikad@worldnet.att.net]
> ..Sent: Sunday, June 24, 2001 8:47 AM
> ..To: alt-photo-process-l@skyway.usask.ca
> ..Subject: Re: Pyro and staining
> ..
> ..
> ..Ken, this is only a guess on my part, but the pyro developer not staining
> ..your collodion negative is probably due to the fact that the image side of
> ..dry plates and modern film is composed of a gelatin emulsion. The
> ..wet plate
> ..image is not an emulsion but a collodion film that has the silver
> ..deposited
> ..on it in a microscopic layer. It seems that the gelatin is a needed
> ..ingredient to achieve the stain your looking for. You had also
> ..recently made
> ..mention of sulfur being needed in a photographic emulsion as
> ..George Eastman
> ..had found out with his failed formula. This seems to hold true
> ..for a gelatin
> ..emulsion but I doubt it has any value when it comes to wet collodion
> ..imaging. Just my opinion. It couldn't hurt to experiment other than maybe
> ..some wasted collodion.
> ..Mike
> ..
> ..----- Original Message -----
> ..From: "ken watson" <watsok@frii.com>
> ..To: <alt-photo-process-l@sask.usask.ca>
> ..Sent: Friday, June 22, 2001 11:15 PM
> ..Subject: Pyro and staining
> ..
> ..
> ..>
> ..> I tried developing a collodion negative using pyro, not a gelatin based
> ..> one. I even tried to "stain" my negative by soaking it in the developer
> ..> after fixing to try and build up a stain. None occurred.
> ..>
> ..> While Pyro helped build density I suspect the staining folks
> ..talk about is
> ..> in the gelatin vs being associated with the image "silver".
> ..>
> ..> So here is my conjecture.
> ..> If Pyro staining is associated with the image why does it not stain
> ..> collodion negatives?
> ..>
> ..>
> ..
>
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