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

[EJ Photo]

Terry, It may be that your experience doesn't support the FO and AFO
printing difference and that's fine but most users will see a difference in
the print. Sometimes the differences are quite obvious and sometime not. 

Also the making of FO can be done in many ways. I haven't seen the speed
drop you speak of either. Direct liquid FO made in my lab hasn't been a
problem an din case after case, out performed B&S fresh mix powered made
time and time again for speed and density. Preparation of chemicals can be
much like cooking; the ingredients and the recipe can be the same but to
chef will still deliver a meal with different taste. 

Eric 

Eric Neilsen
Eric Neilsen Photography
4101 Commerce Street, Suite 9
Dallas, TX 75226
 
www.ericneilsenphotography.com
skype me with ejprinter
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Let's Talk Photography
 
-----Original Message-----
From: alt-photo-process-list-bounces at lists.altphotolist.org
[mailto:alt-photo-process-list-bounces at lists.altphotolist.org] On Behalf Of
Terry King
Sent: Saturday, July 24, 2010 7:22 AM
To: alt-photo-process-list at lists.altphotolist.org
Subject: [alt-photo] Re: dilution of pt/pd

Loris  


I am afraid that the evidence does not support your contentions.



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.


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..


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. 


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.


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.


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.


Terry







-----Original Message-----
From: Loris Medici <mail at loris.medici.name>
To: The alternative photographic processes mailing list
<alt-photo-process-list at lists.altphotolist.org>
Sent: Sat, 24 Jul 2010 12:16
Subject: [alt-photo] Re: dilution of pt/pd


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.
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