From: Judy Seigel (jseigel@panix.com)
Date: 10/12/02-09:43:05 PM Z
My guess is the problem is your ferric ammonium citrate, which tends to go
off, can even arrive "off" from the factory -- as I've mentioned several
times. At school some years ago we got 3 jars of bad fe am cit in a row
from a major chemical company. Finally had to switch vendors to get a good
one.
In my experience it has little or nothing to do with the age of the
chemical -- like people, who can be off at any age ! As it happens, I
mixed up cyanotype today for some negative tests. The fe am citrate was
from a plastic container from Artcraft that's many years old. The
solution looked a little darker than I felt comfortable with, but was
bright yellow-green on the paper & worked fine. (I thought the dark might
anyway have been from adding a couple of drops of thymol -- to see if it
would prevent the usual mold.)
In my experience the moment of truth is when you combine parts A & B. When
the fe am cit is bad the blue precipitates out instantly. If you're
combining the two and they DON'T precipitate out, that is, don't turn blue
until you put on the paper -- hmmmm.
It does sound like it could be the paper -- or even the applicator. Is it
a buffered paper? Cyano doesn't like alkali. Acid is OK. One other
thought comes to mind-- I have a recollection of cyano turning blue on a
cheap pulpy paper, which we figured had some kind of alum in it.
I've also had bad potassium ferricyanide, but that didn't turn the
solution blue -- it simply made a very pale print. One year Kodak sent
out yellow lumps instead of the "ruby red," & we had several jars of it at
school. The rest of the department, using it for bleaching, didn't
notice, because they'd just use a little more, or a little longer, but
mixing a formula with a set amount, the print came out very pale. (That
was my first year of teaching --a scary opener.)
In any event, the k ferricyanide I used today was even older than the fe
am cit. It had gone kind of orange at the top of the jar, but I dug down
a ways & it got redder.
PS. The bad ferric ammonium citrate gave absolutely NO visual clue before
putting in water. The powder in the jar looked fine -- green and dry.
cheers.
Judy
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