Re: odd cyanotype behavior

Others may have a better answer for you but I would suspect that it has to
do with the buffering agent in the paper. I have noticed the same thing with
several papers I have and it seems to only happen to papers with calcium
carbonate as a buffering agent in them. Cyanotype, especially New Cyanotype,
likes an acidic paper. You might try soaking the paper in an 1% oxalic acid
bath prior to coating or try adding a few drops of 40% citric acid to each
ml of the sensitizer.

Hope this helps, Scott

swphoto@verizon.net

----- Original Message -----
From: "ryberg" <cryberg@comcast.net>
To: <alt-photo-process-l@sask.usask.ca>
Sent: Wednesday, May 25, 2005 6:27 PM
Subject: odd cyanotype behavior

> Locally there are several brands of inexpensive, good quality cold
> pressed watercolor paper available. However, I usually prefer the
smoother
> surface of hot pressed paper which is, at least where I shop, only
available
> in large (and more expensive) sheets. I tried a paper called #234 PARIS
> BLEEDPROOF PAPER FOR PENS BY BORDEN AND RILEY. After a couple of test
> prints I made what looked like a perfect print but I was called away and
let
> the print soak for about an hour. When I returned the print had faded
> drastically and lost all its blue color, leaving a gray image.
> I soaked a print on a different paper that long and longer with no
loss
> of image so I assume it is something to do with the paper. Has anyone
ever
> noticed this kind of behavior?
> Very preliminary tests indicate that the pale gray image might tone
up
> to a darker image in one or more of the common acids. Any thoughts?
>
> Charles, Portland Or.
>
Received on Wed May 25 19:36:48 2005