Re: New Cyanotype

From: "Gordon J. Holtslander" <holtsg@duke.usask.ca>
Subject: Re: New Cyanotype
Date: Wed, 19 May 2004 23:15:12 -0600

> I've always suspected thay cyanotype is very sensitive to the pH of paper.
> Is there a standard way of checing the pH of paper. I don't have a pH
> meter, but I have plenty of litmus paper.

It's sensitive to the pH of the coated layer, that is very likely.
For primary photochemical stage of cyanotype-type reaction, see

Abrahamson, H. B., Rezvani, A. B, and Brushmiller, J. G. 1994.
Photochemical and spectroscopic studies of complexes, of iron(III)
with citric acid and other carboxylic acids. Inorganica Chimica Acta,
Volume 226, pp. 117--127.

On top of this, you have the issue of ammonium ion from the ferric
ammonium citrate, and also the pH dependency of the secondary process
to form Prussian blue. My guess is that the optimal pH is shifted or
widened upward. If I were a regular cyanotype printer, I'd do a couple
of hours of search for a good buffering system that doesn't interfere
with the process, and use it. (That's probably just me. I hate
mysteries and I don't like continual attention for the too many little
things during ongoing work...) But guessing from the fact that this is
not customarily done, there is some technical difficulty that I don't
know about?

About the measurement of pH of paper, according to my paper reference,
there's such thing as ISO6588:1981, and other standards, but I don't
know much more.

--
Ryuji Suzuki
"You have to realize that junk is not the problem in and of itself.
Junk is the symptom, not the problem."
(Bob Dylan 1971; source: No Direction Home by Robert Shelton)