Auteur: Philippe Ayral
Date: 12-02-2005 20:50
Je colle un condensé repris du forum pure-silver:
The recommendation to use diluted KRST for protection comes from a paper
by Lee, Wood, and Drago of Kodak, published many years ago. IPI discovered
about ten years ago that microfilm trated with KRST was developing "red
spots" or redox spots. They carried out extensive experimentation and found
that the protection in the Lee, Wood, and Drago experiments was evidently
due to incidental sulfiding of the silver by some impurity in the Selenium
toner. Current production toner does not have the impurity so doesn't
provide the image protection. IPI has a special polysulfide toner for
microfilm but it doesn't seem necessary to use it for prints or ordinary
pictorial film.
Selenium toning does provide some protection even when not complete.
_Full_ toning in Selenium does protect the image as much as sulfiding but
the color change may not be acceptable for some images.
More when I get things together.
I strongly recommend reading Dr. Nishimura's posts to the
rec.photo.darkroom group in the last couple of weeks.
----
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com
Ceux qui connaissent Richard savent l'étendue de sa science…
La version US de notre Emmanuel B.
Philippe
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