Re: tonal inversion and pigment loads

On Jan 27, 2006, at 7:16 AM, Jack Brubaker wrote:

> It is exciting that these issues are getting serious attention.
> It is too
> soon to rule out any possibilities.Tom's observation that the
> grains of
> pigment are moving in a puddle make me wonder if it is possible
> that static
> electricity might be a factor.

Well, static electricity may well be a factor in holding the pigment
to the substrate; I'm certainly convinced that it was what held the
inversion I made on glass, to the glass, and that might explain why
pigment stain holds onto sized paper even though there's no hardened
gum to hold it in place, which puzzled me. It was obvious that the
inversion I got on glass (black letters where white, or clear in the
case of glass, letters should be at the top of the Stouffer tablet)
was constituted entirely of lamp black pigment, not hardened gum,
because it wiped off easily with a fingertip or a tissue, whereas for
me, hardened gum has to be scraped off glass with a sharp razor blade
and sincere effort. That's the point at which I became completely
comfortable saying that the inversion is just another kind of
pigment stain, when I saw there wasn't anything there but pigment.
And the fact that Tom has looked closely at his inversion and found
it made of clumps of loose pigment, just provides more support for
that comfort.

> I apply powder (pigment in small grains of
> plastic binder) to my metalwork via a static electric powder coating
> process. It is amazing how little charge is needed to aggressively
> hold the
> powder in place on the metal substrate. The Xerox process perfected
> the
> photocopy use of light and static charge. Perhaps there is some
> weak static
> charge generated in the environment under the darker areas of the
> negative.
> That the grains are loose in a puddle doesn't sound like a hardened
> gum from
> heat having crosslinked the gum. But, perhaps some combination of
> heat and
> other factors causes the beginning of a weak crosslink coupled with
> a static
> charge. The above are wild guesses for the sake of continuing the
> dialog.

Naw, there's no crosslinking here, just plain old pigment stain. IMO.
Katharine
Received on Fri Jan 27 10:13:42 2006