From: Judy Seigel (jseigel@panix.com)
Date: 04/19/03-12:51:32 AM Z
On Wed, 16 Apr 2003, Katharine Thayer wrote:
> ... A particular pigment, with a particular
> number, has a particular chemical composition and as a result,
> particular properties and characteristics. There are very few
> manufacturers and purveyors of pigments in the world; the difference
> between a particular pigment from one manufacturer or another is like
> the difference between table salt labeled with the Morton's brand and
> table salt with some other brand name on it....
Aside from the fact that different salt brands have different ingredients
(iodides added or not, and some with starch to prevent sticking, that we
know of, and whatever it is about "sea salt" called for in various
recipes) pigment is a more complex compound than sodium chloride. Which
is to say, the analogy does not hold. It doesn't hold in theory and IME it
doesn't hold in fact.
When I tested some 8 brands of burnt sienna, all supposedly bona fide
burnt sienna, all from major manufacturers, American and European, I found
no two exactly alike. (There were in fact more manufacturers, but I got
tired of the game.) Most were distinctly different colors, and exposed and
developed differently, printed with different densities, and showed a
different number of steps, even with all other variables the same.
> As to all the fillers and extenders and whatnots, you find
> those more in the student grades and other lesser types of paint; most
> fine artist quality paints have little or none of this gunk in them and
> tend to be pure gum and pigment, sometimes with honey added to retain
> moisture, but otherwise no extra stuff.
Again, this is said with great authority, but is not my experience. I
have for instance found distinct differences in "major" brands of
so-called "artists' water colors" in covering power (presumably although
not necessarily pigment concentration) and staining (presumably dispersal
or other "agents"), not to mention such other behavior as the "reverse
ladder" noted previously.
Judy
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