[alt-photo] Re: dilution of pt/pd

[Loris Medici]

Terry,

2010/7/24 Terry King <terryaking at aol.com>:
> ...
> The results of our tests show that it makes no difference whether you use ammonium ferric oxalate or ferric oxalate in making
> platinum prints. These and other circumstances have led myself and others, including those with great chemical expertise, to
> doubt Dr Ware's chemistry even if that is lese majesty.
> ...

In fact, there are considerable differences between FO and AFO:
1. FO gives a whisper image and needs development, whereas AFO gives
full print out (unless the wheater is excessively dry) and doesn't
need a developer.
2. You almost never experience solarization with AFO + pure Pd metal
soln. (because of self-masking), whereas solarization is more a
problem with FO sensitizer when using a metal solution with just Pd.
3. AFO sensitizer never goes bad, whereas you have to pay attention to
use relatively fresh FO (not older than 3 months, max. 6 months... And
there are practitioners who prefer to mix fresh soln. in small amnts.
beforehand / per ), in order to avoid fog. Or, adulterate FO after
some time, in order to convert Fe(II) to Fe(III) - which is a PIA!
3 1/2. Related to 3, dissolving FO is even a greater PIA, it's a
relatively slow and complicated process (=hours, heating etc.) whereas
AFO dissolves in a snap...
4. With AFO, you always get the same compound regardless the
production batch and/or supplier, whereas the composition of FO may
change from batch to batch and/or from supplier to supplier. (Which is
something to consider, if you opt to carefully / painstakingly
calibrate your negatives to the process...)
5. And more... (Which I may have forgotten to bring into consideration.)

IMPORTANT / N.B.: All of the above wasn't ment say "AFO is better than
FO", or the opposite. The sole purpose was to list the principal
differences between the two ferric salts we use in pt/pd printing...
Each practitioner has their own "well considered" preference for the
ferric salt they use, and no one is criticizing and/or doubting those
personal preferences here!

Regards,
Loris.