From: Cor Breukel (cor@lumc.nl)
Date: 01/04/01-02:37:54 AM Z
Sarah Van Keuren wrote:
What I still wonder is why
> in vandyke printing, it is very dilute fixer that darkens what is basically
> a rusty reddish iron print by reducing silver salts to metallic silver.
...Sarah AFAIK right now I do not think an VDB image contains iron, only
metallic silver. This metallic silver is formed after reduction of
silverchloride by the light sensitive AmmFerricCitrate. Fixing will
remove the silverchloride molecules. I seem to recall that the actual
removal of the "unexposed" SilverChloride is causing the colour change.
By this removal the metallic silver atoms rearange themselves, resulting
in a diffeferent pattern, thus resulting in a different colour. The
metallic silver particles are relatively very small, and vunarable to
enviromental attacks (such as fixer).
I hope I made myself clear, and did not mix up things, my
"references"are not here right now,
Best,
Cor
Does
> the iron print remain beneath the silver or are they bound together? What is
> the role of tartaric acid - to remove highlight stains or to facilitate the
> mingling of silver and iron? Why doesn't EDTA work with vandyke to remove
> residual iron? I will be home until tomorrow afternoon if you can get back
> to me.
>
> Thanks, Sarah
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