From: Katharine Thayer (kthayer@pacifier.com)
Date: 04/02/03-06:15:43 AM Z
It seems several things are being confused here, so in an effort to
promote clarity, maybe it would help to separate them out.
1.Pigment Staining
1a. Are there pigments that reliably stain in watercolor painting? This
question came up, as I recall, because Christina was trying to separate
pigments into staining and nonstaining as part of her investigations
into staining in gum printing. In other words, I believe she was
starting with the assumption that some pigments are more staining than
others in and of themselves, before proceeding to the question of how
this relates to gum printing. There seems to be more difference of
opinion on this question than I would have thought, but since at least
Judy and I agree that whether pigments stain in watercolor has little
relation if any to whether they stain in gum printing, maybe it's one
of those questions that will never be resolved and aren't worth the
effort of trying to resolve, since they don't relate materially to our
concerns. I personally would take Winsor & Newton's ratings of any
pigment characteristic with a shaker of salt, but that's just me.
1b. Are there pigments that reliably stain in gum printing? Judy and I
have both answered this question in the negative. To repeat myself ad
nauseum, it's just a matter of understanding the individual
pigment/brand combinations. As Mary Pat and others have said said
earlier, sizing probably also plays a role, but in my experience that
matters more with some papers than others.
2. Covering power: In my understanding, this has to do with opacity, and
is a separate issue from staining. Covering power has to do with
whether the color covers the color underneath, or not. In transparent
gum printing, covering power is something you wouldn't want, because in
transparent printing, particularly transparent printing involving
different colors, you want the layers of color to shine through each
other and blend into optical color blends. In opaque printing, covering
power is a quality you would want, I surmise. Since I've always and only
been interested in transparent printing, I am interested only in
transparent pigments, but this is a matter of individual aesthetic
preference.
3. Lifting, which I understand to mean whether a color, when dry, will
stay put when other colors are glazed over it, or will re-wet and mix
into the subsequent colors in an unwanted manner, sometimes resulting in
muddy color mixtures. IMO, this is not an issue in gum printing, since
if properly hardened, the pigment underneath will not be disturbed by
subsequent layers.
4. Tinting strength. In my experience, it's the pigments with the
highest tinting strength that create the most potential staining
problems for novice gum printers, and it's a matter of understanding
that with these pigments, a little goes a very long way. But again,
tinting strength and staining capacity are different issues; perhaps
Christina can discover how the two issues are related to each other.
Katharine
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