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

I suspect the exposure time was wrong - the gum hadn't hardened enough to
retain the pigment. you probably got staining because of the gum dilution -
you didn't need to add the extra 10 ml tapwater. The flaking is probably
caused by too thick a coat/underexposure.
I use around equal proportions of gum and ammonium dichromate. Pot di
carries less chemical in a saturated solution so need more exposure than amm
di. If you double-coat the paper it would also need extra exposure - the
trick with gum is a THIN emulsion, but repeated printings to build up
density. I never size with dichromate so I don't know what effect this would
have.

Kate Mahoney
----- Original Message -----
From: "Loris Medici" <lorism@tnn.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Saturday, November 01, 2003 1:19 AM
Subject: Gum - dichromate sizing and Cyanotypes. Your experiences?

>
> 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.
>
> I sized the papers by using 5ml saturated (%10) Potassium Dichromate
> solution + 10 ml Gum Arabic + 10 ml *regular tap water*? (the dichromate
> solution was also made with regular tap water) and then exposed to UV
> light for 5 minutes and washed the sized papers around 10-15minutes.
>
> I double coated the gum-dichromate sized papers, everything was fine for
> the first coat; it dried nicely but I lost half of the papers (2 of 4)
> end of the second coat due to strange blue-violet staining which showed
> up during drying.
>
> 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?
>
> Regards,
> Loris.
>
>
Received on Fri Oct 31 17:12:19 2003