From: Jack Brubaker (jack@jackbrubaker.com)
Date: 04/19/03-03:55:39 PM Z
As to consistance of powdered pigments...
The earth colors are a lot like the ingredients my potter friend uses. He
makes all his clay bodies from scratch, buying industrial grade clays and
bulk ingredients that he mixes together to get the clay quality he wants.
Every few years a company will close a mine or go out of business. Each time
he has to change to the "same" product from another provider his whole
chemistry changes and he must try several suppliers and alter the mix to
approximate the same result. The suppliers all claim that their product is
the try material and the same as the classic ingredient. Earth colors are
subject to the local nature of their origin. Each will have different trace
elements or be similiar looking but utterly different chemically. There is
no one source for these powders. Every culture has historically pursued
these materials and many still produce their regonial favorites. They find
their way into the world marketplace and show up at out suppliers with
little regard or knowledge of their sources. In fact we may sleep better at
night not knowing what slaves died trying to get our colors out of some
third world whole in the ground.
Jack
> From: Judy Seigel <jseigel@panix.com>
> Reply-To: alt-photo-process-l@skyway.usask.ca
> Date: Sat, 19 Apr 2003 02:51:32 -0400 (EDT)
> To: alt-photo-process-l@skyway.usask.ca
> Subject: Re: Mixing a light pigment for gum
>
>
>
> 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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