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Re: Selenium



At 07:07 PM 07/27/2000 +0100, you wrote:
>--- Judy Seigel <jseigel@panix.com> wrote:
>
>"Kodak polytoner has no fixer in it, and is a mix of
>liver of sulfur and selenium, actually adding more
>archivality than plain selenium."
>
>Uh..., do you have a reference for the "...actually
>adding more archivality than plain selenium..." part
>of this comment?
>
>Thanks,
>
>R.M.
>
  The use of diluted Kodak Rapid Selenium Toner for protection of silver
images became widely recommended and used due to research at Kodak labs in
the mid 1960's. The usual recommendation was to treat prints for a few
minutes in a 1:20 dilution. 
  About ten years ago, the Image Permanence Institute discovered that
microfilm treated with this toner in the recommended way had developed
redox spots and other indications of attack by atmospheric gasses. Their
research found that the Selenium treatment was ineffective. The Selenium
toner used for the original research evidently was evidently contaminated
with something which caused incidental sulfiding of the image. It was this
incidental sulfiding which was responsible for the image protection. Images
which are _fully_ toned in Selenium are archival, the silver selenide being
as stable as silver sulfide. However, a toner of the Kodak type tones the
finer grains of silver in the denser parts of the image before it tones the
highlights, so toning for a short time in diluted Kodak selenium toner does
not provide full image protection. Dr. Nishimura of IPI recommends KRST be
used at not more than 1:9 dilution and that for three minutes minimum at
68F. IPI also found that the protection given by Kodak GP-2 Gold toner was
also due to incidental sulfiding and not to the Gold.
   I am being specific about Kodak Selenium toner because I don't know if
the split toning effect is specific to it or to Se toners of all types.
  IPI now recommends treatment of microfilm with a modified polysulfide
toner similar to Kodak Brown Toner. The IPI Silver Lok toner is
specifically formulated for microfilm treatment and may have no specific
benefit for general use. Kodak Brown Toner can be used but beware of
diluting it too much. This type of toner has the odd effect of working
faster as it is more diluted, and as it becomes more exhausted. If used in
very high dilutions it causes a peach colored stain in highlights. So, it
should be used in fairly strong concentration. Even very slight toning with
it gives full image protection. After toning it should be "stopped" in a
bath of undiluted Kodak Hypo Clearing Agent and washed rapidly. The rapid
washing, at least at first, is to prevent continued toning as the toner
becomes more diluted. The same peach colored stain can occur from too slow
washing. 
  Poly Toner is a mixture of Brown toner and Selenium toner. It should
result in very permanent images but was not specifically discussed in the
IPI paper. 
  Images _completely_ toned in a sulfiding toner or in Selenium toner are
very permanent. The problem is with very slight toning with highly diluted
KRST. 
  For details see the IPI paper on the Conservation On Line web site at
http://palimpsest.stanford.edu  Do an author search for Nishimura for this
and several other interesting papers and letters.  
----
Richard Knoppow
Los Angeles,Ca.
dickburk@ix.netcom.com