Katharine Thayer wrote:
>
>
> I tried my darnedest to find a tube of
> > chrome yellow (PY24)
>
> to test the old adage that chrome colors affect the
> > process adversely, but to no avail.
>
> I've used viridian and chromium oxide green, both chromium paints, with
> no problem. I'm convinced that's just another myth.
>
P.S. My personal take on this is that the myth is based on an inadequate
understanding of the chemistry behind the process. I suspect that
someone at some point said well, if irradiated chromium reacts with gum
to insolubilize the gum, then any chromium in the presence of gum and
light must do the same. And then everyone along the way just repeated
that. But in fact the chromium in the pigments is in a stable form (III)
with regard to light, and so is inert with regard to the process.
I suppose an argument could be made that the chromium oxide could work
something like chromium sulfate in chrome alum, hardening in the absence
of light, but in my own experiments I haven't found chrome alum very
effective in hardening gum, and at any rate I haven't ever heard that
chromium oxides work the same.
kt
Received on Wed Jun 1 11:41:06 2005
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