I apologise to Philip for sending this to him rather than to the list.
-------------Forwarded Message-----------------
From: Terry King,
To: Philip Jackson, INTERNET:pjackson@nla.gov.au
Date: 09/12/96 21:58
RE: RE: Judy's Ferric Ammonium Citrate Puzzle
Message text written by Philip Jackson
> the only benefit to making
your own, assuming every step involved was perfectly safe, and could be
precisely repeated, might be to ensure it really is the same stuff every
time, and therefore behaves predictably.<
I had always assumed that the brown ferric ammonium citrate was brown because it
had been exposed to light. And that was why it did not work as well.
There was a time recently when the main purchaser of ferric ammonium citrate in
the form apparently best suited to the needs of those making cyanotypes and
kallitypes decided to add the chemical to his foodstuff using a different
method. Since then the material available has not been as pure or as consistent
as one would wish. The good stuff is like green pea flour.
As FAC is the basis of the two easiest and cheapest alternative processes,
kallitype and cyanotype, which both produce prints of great subtlety of tone and
gradation that give a satisfying and exciting introduction to the newcomer, it
is important to us all to have a reliable supply that will do the job.
I asked if anyone knew of a method of making FAC at home. I now find that my
newly purchased copy of Woodbury's 1890 Encyclopaedia of Photography gives the
following recipe for making ammonio citrate of iron:
"Dissolve ferric oxide in citric acid and add liquid ammonia .880 until the
solution becomes neutral."
Any comments on the practicality or the amounts and the likely strength of the
'neutral soluton' ?
Taking Philip's point about exposing FAC by itself, if you coat paper with a 10%
solution and print out as far as possible and then develop in a 1 % solution of
hydrogentetrachloroaurate, you get a great gold print. But it is a one shot
process.
Terry King