Judy Seigel (jseigel@panix.com)
Mon, 19 Jul 1999 21:30:20 -0400 (EDT)
On Mon, 19 Jul 1999, Tom Ferguson wrote:
> > 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.
You don't say if you had started a new bottle of any of the chemicals
at the point where the trouble began.
You also say "appearance of fogging" -- but not if the print itself fogged
when made. In very warm weather (where are you???? NYC????) and high
humidity, emulsion can go blue on the paper but may still print OK.
I also had a jar of fe am cit (green) that was bad upon opening. Turned
blue as you describe. A replacement from the same company was ALSO bad.
Got a new jar from a different company was OK.
At that time Mike Ware advised adding a certain % of a very dilute
potassium dichromate to the emulsion -- it did clear up the pre-fogging,
but the contrast was through the roof, times much slower, and loss of grey
scale made an inferior print.
My own tests, BTW, showed that classic formula without either dichromate
or oxalic acid worked best...
The emulsion with the oxalic goes off sort of (again -- in my tests) after
about 6 weeks -- but some tests (not yet completed) of VERY old emulsion
(like 2 years) show it kept *on the paper* better than the plain -- like
for about 2 weeks. In other words, there are so many variables it's hard
to make generalizations, but tests both I and my students made suggest
wait a day or two for fresh emulsion to get its full strength, then test
again after, say, 2 weeks if you're in habit of working from 21-steps
rather than test prints (as we do).
good luck,
Judy
>
> 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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