Re: Gum - dichromate sizing and Cyanotypes. Your experiences?

On Fri, 31 Oct 2003, Loris Medici wrote:

>
> I tried to gum - dichromate sizing on a paper which works well with
> cyanotypes; because I wanted a dichromate stained background and *extra
> clarity/definition*? due to above-the-paper pigmentation caused by the
> heavy sizing.
>
> And when I developed the exposed prints they cleared very quickly in the
> first wash but they continously relesed prussian blue to water on the
> subsequent washes. The prints never stopped releasing prussian blue to
> the wash water - even if they started to fade (I gave them a short
> hidrogen peroxide wash too)... What have I done wrong? Preparing
> dichromate solution with tap water (cyanotype chemicals are with tap
> water too)? Coating twice? ???
>
> Can you please share your experiences with gum-dichromate sizing and
> cyanotypes?

My guess would be that no tinkering will give you a really good cyanotype
with size added to the paper, especially not a gum size, which has more
body & sits more on the paper surface than for instance a gelatin size,
and even gelatin size is bad bad bad for cyanotype. Certainly my tests
showed that NO added size made as good a print as cyanotype directly on
no-added size paper, and many were terrible.

The reason would be that, unlike a gum print, which can if you insist go
over a gum size, sitting as it does ON the paper, a cyanotype emulsion has
to soak into the paper... Cyanotype doesn't get hardened as gum does by
light, it simply exposes. If you have a hardened surface on the paper, it
can't sink in and odds are will flake off.

If you want to make a cyanotype on a dichromate colored ground, try some
other strategies. I'd start with just very dilute dichromate exposed
without gum or a very dilute palladium emulsion exposed, or possibly a
permanent dye. On some papers vandyke brown will hold under cyanotype tho
on others the ferricyanide bleaches it out.

good luck,

Judy
Received on Sat Nov 1 18:24:56 2003