>Mr. Ware, I believe I've read an article by you in View Camera magazine
>describing the ammonia-based Platinum process. Has this ever been tried on
>Kallitypes? Any chance that it may work? Love to hear about that.
(Please call me Mike) - No, the recent article in View Camera was by my
friend and one-time collaborator, Pradip Malde; although he makes a
generous acknowledgement of my part in our work on the ammonium-based
platinotype process.
In answer to Adam's questions: yes, I have tried it; and no, it doesn't
work (at least, not well). The besetting problem of the Kallitype process
is the precipitation of silver oxalate from the sensitizer solution, as
Dick Stevens so clearly pointed out in his recent comprehensive book
'Making Kallitypes'. If you use ammonium ferrioxalate instead of ferric
oxalate, the relative concentration of oxalate ions is even higher, and the
precipitation worse. This is a case where ferric oxalate is more desirable,
indeed with added ferric ion (as ferric nitrate) to suppress the free
oxalate concentration further, as Dick Stevens discovered. Even so, slow
precipitation will occur.
So far, I have avoided this problem altogether by devising the Argyrotype
process, which uses ammonium ferricitrate - but it remains as a challenge
to chemistry!
BTW Adam, are you sure that the stuff that you bought so cheaply wasn't
ferrous oxalate (aka iron(II) oxalate), which is usually obtainable as a
dihydrate: FeC2O4.2H2O? Ferric oxalate (aka iron(III) oxalate) is
Fe2(C2O4)3.6H2O, althought the water content is slightly variable, as I've
said. (Sorry the ASCII character set can't do subscripts.)
Mike