From: Bob Kiss (bobkiss@caribsurf.com)
Date: 06/30/00-08:26:58 PM Z
DEAR LIST,
Yesterday I received info directly from the IPI comparing selenium and
sulfide toning.
It was stated that selenium toning CAN be as effective as sulfide toning in
protecting sliver images IF the toning is sufficient. That coincides with
Richard's info suggesting that the concentration be greater than 1:9 (KRST
TO H2O OR WKG HYPO CLEAR) and, indeed three minutes MINIMUM. It appears
that, while sulfide toners effect all density ranges equally, selenium seems
to coat the silver grains in the high density areas more than in the low
density areas. This isn't a surprise as we know that selenium toning
significantly increases the D-Max while barely affecting highlight density
and that the effect is more than merely proportional to density. We also
know that prints usually show the effects of degeneration first in the
highlights.
Hence we must be certain that the highlights are well toned as well;
ergo the higher concentrations and longer times. So let's not yet throw out
the selenium baby with the wash water...as it were :-) The 1:20 to 1:40
recommendations on the KRST labels are, therefore, not really the best for
archival permanence.
Though it seems fashionable to bash old Ansel for his myopic aesthetics
we must give him credit for stating in the 1960s edition of his book, THE
PRINT, that optimum preservation was achieved with selenium toner
concentrations of (if I recall correctly) between 1:5 and 1:10.
On this note...good night, bonne nuit, boa noite, buona notte etc., etc.
CHEERS!
BOB KISS
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