From: Sandy King (sanking@clemson.edu)
Date: 10/31/03-09:17:26 AM Z
Ryuji Suzuki wrote:
>
>Also, if the experiment used the same bleach bath for all samples,
>this is another possible source of error. Hexacyanoferrate (III)
>becomes hexacyanoferrate (II) after participating in bleaching
>reaction. The presence of the latter reduces oxidation potential of
>the bleaching bath. (It is a well known trick that if ferricyanide
>bleach is too vigorous for a particular application, add a bit of
>ferrocyanide to tame the activity. Dilution works, but in a slightly
>different way.)
Just for the record, I mixed a fresh batch of working solution for
each of the 4X5 prints that were bleached.
>Anyway, I think enough has been said about how challenging it is to
>measure amount of a specific metal in a complicated configuration.
>--
I have to agree with this, and may I add that I am somewhat surprised
how little valid literature there appears to be on the subject of
toning. Or for that matter, how little is understand of the exact
nature of the reaction.
However, let me say that what I have already found has satisfied my
particular interest in the subject, at least for the time being.
Namely.
1. Toning a silver image with palladium will not entirely eliminate
silver in the print. And if *any* silver remains in the image I would
consider it inappropriate to call a palladium toned kallitype prints
as just a palladium.
2. Toning a kallitype with palladium is highly effective in
protecting the print from oxidative processes. The fact that a
palladium toned kallitype retained such a high percentage of its
actual visual density after ten minutes in a strong bleaching bath is
to me really quite impressive. And since the issue at this point is
image permanence the question of whether the silver has been replaced
or plated is not especially important.
Sandy King
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