> Very interesting!
>
> Makes a lot of sense. A soft bottom layer with a hard top layer. Since the
> problem of any direct process is that the development is from the bottom.
> In this way you can easily get flaking. I would expect the pigment to be in
> the bottom layer, but sandwiched in between seems logical as well. The
> thick hard top layer functions to hold back the flaking. If the top layer
> is really really hard then the dichromate will have little effect on it.
> The trick is then how to get the developed soft stuff from underneath to
> wash free from the image during development? Say for instance the paper was
> laser perforated all over, this would leave little wells for the pigment to
> escape through leaving the hard top layer protecting the image from
> flaking. May piercing through the back with a zillion microscopic holes
> just up to the first layer of pigment?? Another idea would be use some kind
> of abrasive material during development. Maybe sawdust?? <grin> The idea of
> the sawdust would be to break the hard upper crust and free the pigment
> from the developed bottom, and not really not to develop out the whole image.
>
> The final powdering of the pigment is a mystery?? . . . . . . . . . . .
> . . .
Now try to figure in that the dichromate would harden from the surface of
the coated paper down toward the paper substrate and in proportion to the
light exposure. A laser holes or abrasive leaves a gap in the logic.
> >
> >According to the analysis, the Fresson paper in question consisted of the
> >following, in this order:
> > 1. a paper base, followed by
> > 2. a thin coating of soft gelatin with a relatively thin black pigment
> > dispersion, with a slight cool, ultramarine tone, followed by
> > 3. a thicker layer of gelatin, harder than the first, with no pigment,
> > followed by
> > 4. a powdering of a very fine, dry pigment
> >
> >Hope this information proves interesting to some of you.
> >
> >Sandy King
What about another tack on how the paper might work. What if the colloid
were not gelatin but instead one that both hardened and changed adhesive
property on exposure to dichromate and light? Assume that the unexposed
colloid is soluble and very adhesive/tacky and on exposure becomes
hardened and no longer tacky/adhesive. Can anyone shoot this idea down
for some logical or informational reason?
Thoughts and feedback ?
Sincerely, Art
Art Chakalis
Columbus, Ohio, USA