[Alt-photo] Re: DAS

[Charles Berger]

The light restraining effect of dichromate (or DAS) in a  gelatin emulsion
keeps the light from penetrating very deeply into the film regardless of
excess coated film thickness.  Even a clear (no pigment) film with a weak
(say 1%) sensitizer will have far less than a 1 mil depth of hardening.
More sensitizer (or more pigment) will further limit hardening depth .

The apparent "relief"  of carbon tissue has more to do with local
variations in the surface tensions of the processed and dried film layer
than with infinitesimally slight physical differences in d-min and d-max
areas.

Charles


On Thu, Apr 18, 2013 at 12:44 AM, Kees Brandenburg
<workshops at polychrome.nl>wrote:

> Hi Loris,
>
> Once you get used to presensitized carbon tissue with double transfer you
> will see the huge advantages this gives. You can also build up relief by
> printing in layers. You don't need to work with color separations, printing
> two layers of black/medium black on top of each other works great and the
> result can be more powerful than a single layer carbon print.
>
> -k
>
>
>
>
> On 18 apr. 2013, at 09:03, Loris Medici <mail at loris.medici.name> wrote:
>
> > I can understand the need for thin tissue for color work, but (with
> > the exception of gum or gumovers) I only print monochrome, and what
> > draws me to carbon is the relief. I'm quite happy with what I can get
> > from pop pd and/or gold toned vdb/argyrotype...
>
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