Re: Mixing a light pigment for gum

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From: Judy Seigel (jseigel@panix.com)
Date: 04/20/03-11:34:20 PM Z


On Sat, 19 Apr 2003, Jack Brubaker wrote:

> 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.

Jack, I had an experience like that years ago when I painted with acrylic.
Venetian red was a favorite color -- a shade of such intense covering
power that it vibrated: nothing, pigment or mix, could match it. It was
also, like some pigments, a very fast dryer. I don't think it matters in
watercolor, but in oil or acrylics, where the paint is used thick, drying
rates are part of the equation.

Anyway, when the dregs in the jar died I thought it was no big deal-- I
bought another. But the new color (same brand) was a dud... Hue was about
the same, but handled so differently the thrill was gone. The company
explained that the old mine (near Venice, if you could believe !) was
exhausted & they'd changed to another mine a few hills away. I thought
they must have changed the formula. They swore not.

Lost my taste for Venetian red.

I don't seem to use earth colors so much in gum -- at least to date I've
preferred the tranparency, light, and mixing qualities of the "process"
colors, where, contrary to katharine's experience, I have found enormous
difference in working. As was explained to me, the thalos and
quinacridones, et al, are made by soaking a matrix in synthetic dyes, then
grinding them up. When the colors don't mix well in normal watercolor
practice, dispersal agents are added. These may account for differences
between "same" colors... and/or it's the matrix material itself. Whatever,
I've found serious performance differences.

What I don't find, however, is the same dependence on the particular color
-- because, unlike watercolor painting, where you put your dabs of color
on the palette and may dip and flow in areas all by themselves, I rarely
leave an area of a gum print in a single color. Most are mixed, either in
a given coat or on top of each other... I suspect also that unlike acrylic
painting where only water was added, the addition of major amounts of gum
arabic in gum painting, makes that the dominant note.

I can just imagine the dilemma of a potter who has to change materials...
kiln reactions can make ours seem like child's play. Still, I try to back
up an essential material...If I die with an unopened gallon or two of gum
arabic, that's OK. (Like me, it's biodegradable !)

Judy


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