Re: tonal inversion and pigment loads

Hi Tom,

I'm not sure this is in this line of thought but surface tension (the
phenomenon that allow bugs to walk on water amoung others) I think it's
called is a pretty strong force and gravity is certainly no match for it in
the case of micrograms particules of pigments.

Regards
Yves

----- Original Message -----
From: "Tom Sobota" <tsobota@teleline.es>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Friday, January 27, 2006 4:46 PM
Subject: 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 16:01:20 2006