Bill_Lucas (Bill_Lucas@compuserve.com)
Mon, 19 Jul 1999 20:44:00 -0400
Help!
I have been a ten-year user of the cyanotype and gum bichromate photo
processes. Recently, I've run into trouble with the cyanotype. I mix my
own chemistry using the following, traditional recipe:
Solution A:
oxalic acid 1.25 g
ferric ammonium citrate 67.5 g
distilled water 280 ml
Solution B:
oxalic acid 1.25 g
potassium ferricyanide 22.5 g
ammonium dichromate .5 g
distilled water 250 ml
I have always used the "brown" version of the ferric ammonium citrate
without any apparent problems. Lately, however, the A solution took on a
blue color before mixing with the B. The combined color of A and B was
subsequently not the the usual yellow-green. After drying in darkness, the
paper was already blue (as if fogged).
I decided to mix a new batch of both A and B (using "brown" ferric ammonium
citrate again), but ran into the same problems.
Now I have mixed another new batch using "green" ferric ammonium citrate,
but I'm still getting the appearance of significant fogging.
I have always used Arches watercolor and Fabriano Artistico. My drying
techniques have not changed; if anything I have been more careful since the
trouble began to keep incidental light away during the drying and until
exposure. I have tried dim incandescent and tungsten light during coating.
Have either paper makers changed their formulation? Could any of my
crystalized chemicals changed in the bottle? Could retail distilled water
have contaminants (I used to use pruified water from my husband's lab)? Do
the solutions perform better after sitting for a few weeks or months? Have
any other long-time users of cyanotype experienced these problems out of
the blue? ; )
I appreciate any serious input. Art is my livelihood and my sun days are
limited.
Thank you in advance,
Siouxsan E. Miller
e-mail via my husband: bill_lucas@compuserve.com
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