Digital BW, The Print

In addition to educating people about the relatively archival quality of the
best current inkjet pigments, perhaps we should remind the traditionalists
that the selenium-toned silver print may not be as rock solid as they
thought.

In general, silver oxidizes and selenium at the traditional 1:19 dilution
has been found to be rather ineffective.

For a good summary of information and links, see
http://unblinkingeye.com/Articles/Archival/archival.html


The summary of the research that is often cited is at
http://palimpsest.stanford.edu/byorg/abbey/an/an12/an12-5/an12-507.html

Some quotes:

"There are two fundamental mechanisms by which silver photographs
deteriorate: they react with sulfur present in the air or left behind in
processing, or else they fade because of image oxidation, in which air and
moisture (or various pollutants) literally corrode the silver."

"...silver does react with air and moisture--it corrodes, ..."

"In the process, silver forms water-soluble species (silver ions and silver
compounds) and these begin to migrate throughout the gelatin layer.
Ultimately, most of the silver is redeposited in the metallic state, but at
some distance and in a different physical form that it originally was. It is
this physical rearrangement, together with the fact that silver compounds
are largely colorless, that is the real cause of "fading." ..."

" In actual practice, when used as recommended, the metal components of gold
and selenium toners for microfilm do very little to protect against
oxidation; their effectiveness is almost entirely due to the sulfiding
action of other constituents of the toner formulas."

"... surprising ineffectiveness of Kodak Rapid Selenium Toner..."

"Conclusion
Though many silver images have been ruined by poor processing (improper
fixing and washing), a more important deterioration mechanism for the
majority of photographs is image oxidation...."

And, of course, the chances of poor processing and the lack of buffers in
the traditional photo paper are not dealt with in this article, which is
focused primarily at microfilm deterioration.

Paul
http://www.PaulRoark.com