From: Etienne Garbaux (photographeur@softhome.net)
Date: 10/28/03-08:44:36 PM Z
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
This archive was generated by hypermail 2.1.5 : 11/05/03-09:22:18 AM Z CST