Re: tonal inversion and pigment loads

Jack,

Electrostatic charges are a possibility, yes. But you should see it by
yourself! Do you have access
to a stereo loupe or a low power microscope? If not, I'll try to scan
some images and show you.
Not every pigment works, since some are far too finely grounded. But in
the case of Ivory Black,
which is essentially burned and ground bone, the variance of grain sizes
is enormous and some are
large enough to be manipulated with a needle point.

What I did was to put a just developed image, still wet, under a loupe.
And there, in the pits of a
rough grain paper, I saw the grains of pigment moving apparently freely
with the small water
currents produced by the illumination lamp. Other grains were fixed by
the hardened gum.
Fascinating. After half an hour of inmersion in water facing down, these
large and loose grains
should have gone to the bottom of the tray. But somehow, they didn't.

However, how to test for electrostatic charges? Any simple, feasible
idea? Actually it is not
necessary to work with a still wet emulsion. When dry, the grains are
still loose.

Tom Sobota
Madrid, Spain

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. 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.
>
> Jack
>
Received on Fri Jan 27 15:46:52 2006