From: Liam Lawless (liam.lawless@blueyonder.co.uk)
Date: 10/28/03-09:17:22 PM Z
Etienne,
I recall from somewhere that toning (with gold, at any rate) results in
the partial replacement of silver, this silver being converted to the
chloride (taking Cl from the gold chloride) as gold deposition takes
place, and that this is one reason why prints should be fixed after Au
toning.
If so, then maybe a coating of AgCl as well as gold on the silver grains
is another limiting factor, and perhaps toning could be taken a bit
further if toning is continued after a short fix?
Liam
-----Original Message-----
From: Etienne Garbaux [mailto:photographeur@softhome.net]
Sent: 29 October 2003 02:45
To: alt-photo-process-l@sask.usask.ca
Subject: RE: Test for Silver Metal in Print?
Christian wrote:
> the test made by a french chemist known as Glafkidès report that there
> is still about 25% silver in the image after a platinum toning.
I have not analyzed toned kallitypes or van dykes, but I have analyzed
toned salt prints, toned albumen prints, and toned silver POP prints.
In all cases the prints were toned first with gold and then with
platinum. Rather than measure image density, I first separated the image
metal from the substrate and binders, weighed it, dissolved the silver,
then re-weighed the sample. The samples always lost weight, showing
that in no case did gold and/or platinum completely replace or
hermetically encapsulate the silver. Based on my results, I estimated
that silver constitutes 1/3 to 2/3 of the image metal in toned albumen
and POP prints, and 20-25% in toned salt prints. Presumably, the
greater surface-to-volume ratio of the smaller, more numerous colloidal
silver particles in salt prints enhances the replacement or
encapsulation process; however, I found no way to make toning proceed to
a point where the silver was either entirely gone or encapsulated beyond
attack by corrosive agents.
Best regards,
etienne
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