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

[Loris Medici]

Terry,

2010/7/24 Terry King <terryaking at aol.com>:
> ...
> In everyday practice of develop out platinum printing, using the dilutions I have already cited,  there is no difference between
> ammonium ferric oxalate and ferric oxalate.

(%) I would suggest that you practice more or to (at least) try
different practices then... (Epecially if you intend to talk about /
criticize them!)

> ...
> In fact for many years, as I had never experienced 'solarisation' with platinum printing using ferric oxalate, I wondered what people
> were talking about. What did make a difference was using  precious metal solutions that were too weak or papers which were highly
> buffered when there had been no pre-soak in oxalic acid..

Good for you. But, in fact, there are people who had experienced
this... BTW, IIRC, you weren't printing pure Pd - according to a
statement you've made a couple of days ago, therefore your point above
is kinda moot. (Because adding Pt into the coating solution
effectively inhibits this phenomenon...)

> ...
> As I have made ferric oxalate as an exercise on workshops from year to year, I can tell you from the evidence of having ferric oxalate
> of different vintages, that ferric oxalate in solution loses in speed by about a third of a stop a year.   Ferric oxalate, kept in brown
> bottles, as  much as five years old is still perfectly usable given the appropriate exposure.  I suggest that you correct your notes to
> take account of this evidence.

(*) I guess maybe your statement above explains why many of your
prints doesn't show pure whites (I mean where we expect them; e.g.
interior shot, strong daylight/backlight coming from windows, no
detail of the outside) in your (e.g.) Opera Regis -> Platinum gallery
(Church Interiors), whereas some do... (VERY IMPORTANT: I'm not saying
"we absolutely need pure whites and/or pure blacks in photographs",
though! - Please lets not start another pointless discussion from
here...) My guess would be: (a.) It's due to non-light induced /
premature reduction of Fe(III) to Fe(II) causing fog and/or (b.) You
have problems with keeping your negatives' DR constant. (With a little
/ reasonable play...) and/or (c.) Those reproductions are horrible.
(Or - at least - inconsistent.)

> ...
> It is easy to dissolve ferric oxalate, just keep it in a warm water bath and stir from time to time. There are simple tasks in cookery
> which are more complicated.

To me, your internal definition of "easy" is extremely variable /
volatile then...

> ...
> I calibrate my negatives and have had no problems with ferric oxalate using different sources of supply,( apart from having to add
> oxalic acid), and solutions made in class using different methods.

See the latter parts of the section marked with (*) above...

> ...
> There seems to be far too much 'research' to solve problems which do not exist. That has been true over the history of photography
> from 'The Silver Sunbeam' to Mike Ware.

Ignorance is bliss, indeed... (See the section marked with '%' above...)

Regards,
Loris.