Re: tonal inversion and pigment loads

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

> From: Ender100@aol.com
> Reply-To: alt-photo-process-l@sask.usask.ca
> Date: Thu, 26 Jan 2006 20:55:59 -0500 (EST)
> To: alt-photo-process-l@usask.ca
> Subject: Re: tonal inversion and pigment loads
>
> ;)
>
> In a message dated 1/26/06 2:25:15 PM, gauvreau-yves@sympatico.ca writes:
>
>
>> here is an idea, I think it is well known that heat by itself causes some
>> cross-linking to happen and say under a step tablet where the density is
>> high enough, exposure alone doesn't reach the gum but heat does. It could be
>> that heat doesn't transform the gum dichromate in the same way as does
>> exposed gum, in other word the two phenomenon don't "create" the same type
>> of molecule and the cross linking of one may have different properties then
>> the other or something like that.
>>
>
>
>
>
>
> Mark I. Nelson
> www.MarkINelsonPhoto.com
> www.PrecisionDigitalNegatives.com
> PDNPrint Forum @ Yahoo Groups
>
Received on Fri Jan 27 09:17:44 2006