Re: Gum hardening: top down experiment et al

What about making a digital negative using UV-opaque but vis-transparent
dye and print on the other side of the film?

Doubly subbed film may be useful here.

Incidentally, I think one question related to the top-down hardening is
the UV-density of well-mixed dichromated gum with various pigment, per
unit thickness. Based on it, we can calculate the penetration depth
(it'll be an exponential function and we'll be using depth constant, or
half-absorption depth, or some sort of index) and relate this parameter
to the optimal coating thickness, for front exposure system.

On Thu, 13 Apr 2006 17:26:31 -0400 (EDT), Ender100@aol.com said:
> Henk,
>
> an interesting effect for a "gum-over" might be using the PT/PD printed
> image
> as a negative itself and just coating the PT/PD print with a gum mixed
> with
> diluted pigment and exposing from the back.
>
> Mark Nelson
>
>
> In a message dated 4/13/06 2:21:05 PM, henk.thijs@hetnet.nl writes:
>
>
> > Could the info gained by the discussion concerning the 'top dow
> > experiment', also be useful for a process like gum over pt/pd.
> > I mean that one could coat a pt/pd print with a gum-pigment-chromate
> > solution and i.s.o. going through normal procedure with putting the
> > negative on etc., just expose through the back. ; there would be some
> > proportial light reaching the gum-emulsion in relation to the coverage
> > of the pt/pd print, or?
> > I remember vaguely some discussion in the 'old' days of the list, but i
> > could not find something in the archive.
> > Regards,
> > Henk
> >
>
>
>
>
>
> Mark Nelson
> Precision Digital Negatives
Received on Thu Apr 13 15:34:29 2006