Re: yellow pigment for gum

Katharine Thayer wrote:
>
> Christina Z. Anderson wrote:
> >
> > Katharine,
> > I'm working on a chart of the yellow pigments I have used in gum (10 of
> > them, painting swatches side by side). I notice that Wilcox gives the M.
> > Graham old gamboge which was PY110 a not lightfast rating (p. 68 2001-2
> > edition of Wilcox Guide to Watercolor Paints).
> >
> > Obviously this is a moot point since M. Graham reformulated their gamboge,
> > but I notice in my notes that this was a yellow you used, or used to,
> > anyway
>
> so:
> > 1. Do you think Wilcox is wrong?
>
> Yes, as he often is.

But when I pulled out Wilcox to see what he actually says, it seems
that even he is equivocal about the rating he gave it. He says "This
pigment has...now appeared on the ASTM list both as III (not approved)
and I (approved). Until clarification I will stay with the original ASTM
III given my own findings as backup." What I gather from MacEvoy's
tests and from his citation of industry tests, also from Page's rating
of the pigment as I ("excellent") is that the clarification has been in
favor of the I (totally lightfast) rating.

What's also interesting is that the swatch Wilcox shows, which he says
faded, (1) appears to be a very heavy load of pigment, since it's
definitely orange in hue ( IME it's impossible to get this pigment heavy
enough in gum printing to print actually orange) which is odd because
other testers find this pigment to be absolutely lightfast in masstone,
and (2) shows no discernable fading. (he divides the swatch in half so
you can compare one half to the other and see how much fading there is.)
Katharine
Received on Mon Jun 6 09:23:33 2005