Tom Ferguson (tomf2468@pipeline.com)
Mon, 19 Jul 1999 18:00:56 -0700
>From: Bill_Lucas <Bill_Lucas@compuserve.com>
>To: Alt-Photo mailing list <alt-photo-process-l@usask.ca>
>Subject: I'm Blue Over My Cyanotype!
>Date: Mon, Jul 19, 1999, 5:44 PM
>
> 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 too used this version of cyanotype. Many comments on this list
made me wonder if the Oxalic Acid and Dichromate were needed (or
might even hurt). But, I had editioned work I was trying to
match. My results: I can skip the Oxalic acid totaly, but the
dichromeate makes a very slight contrast differance.
My point: try mixing a small amount without these chemicals and
see what you get. Also try getting new (clean) jars (I wonder
what rust on a jar lid does to cyanotype??). Or how about
coating with a differant brush (again rust or other metal
contaminent).
>
> 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?
My experience is that the solutions are better after about 24
hours. Something doesn't dissolve well, and I sometimes get
streaks with too fresh solutions. But, that has nothing to do
with your problems.
Hope this helps.
> SNIP>
-- Tom Ferguson tomf2468@pipeline.com http://www.thefstop.com/tf.html
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