From: Judy Seigel (jseigel@panix.com)
Date: 02/10/03-01:19:21 AM Z
On Sun, 9 Feb 2003, pete wrote:
> In my opinion there are two staing processes at work here,
> one-:the stain produced by the pigment particles themselves for instance
> Phthalocyanine Blue can give massive stain whereas Cerulean blue does not.
I take your word for your pigments, but my thalo blue is one of the
cleanest working pigments I have. I've never used cerulean blue for a gum,
after the first try... no covering power
> And two-: the concentration of the pigment in mixture the more pigment mixed
> in a given volume increases contrast and reduces emulsion sensitivity to
> light, and also at the same time shows a corresponding reduction in the
> apparent pigment stain
What do you mean *apparent* pigment stain? Can there be an unapparent
pigment stain? Whichever, if I follow what you're saying then you too
agree the famous GPR test is rubbish.
Though I don't know what "reduces emulsion sensitivity to light" refers
to.... If you're saying a lot of pigment means you don't get light through
to the base where it's got to harden to hold, so it tends to flake --
that's what Mike Ware explained these 6 years ago & what I've been trying
to point out since then too.
> There is also the dichromate stain at work but that is another story
Dichromate stain is removable... and I doubt related to gum-pigment ratio
(especially without the dichromate).
J.
.
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