> To all Ferric Oxalate users,
>
> Several months there was some discussion as to the availability, and
> quality of Ferric Oxalate.
>
> Brian Miller [Brian.D.Miller@Dartmouth.EDU] graciously sent me a sample
> of the Ferric Oxalate (F.O.) he makes following Fred Foster's recipe. I
> ran a comparison with the Ferric Oxalate powder I get from Bostic &
> Sullivan (B&S).
<SNIP>
Hi Jeff,
I have been running afew test as well. I have received samples of Curt
Ricthers,& Brian Millers formulas. Curt claims his to be 20%, Brian 28%.
And B&S claims 27%. While I did not get enough to run Sp Gr test on all.
I do have enough to run wieght/volume measurments for Curt's and Brian's
vs. B&S and my "home made ferric". I make mine to be 25%. Brian's as
expected did weigh more, and Curt's less. The Sp Gr test done on B&S
indicated only a 22% solution. All had the same relative pH .8 +/- .1.
The speed and contrast changes can be attributed to the different
concentrations, ie. the stronger ferric (Brian's) being faster and
contrastier because it has more ferric ions. (more complete reaction with
less fog)
As to the blue color appearing, I too have had a tough time explaining
it's presence. My last batch did not have any blue color form and it is
working very well. The solution is quite complex and even a mass
spectrometer may not tells us why one works and other does not.
The proof so to speak is in the pudding. If the ferric you use makes
the prints look the way you want them to look good. There is much
experimentation that can be done, but at what point do you stop and just
make prints. I have been conducting experiments usiong the ammonia based
platinum salt with "regular" ferric and " regular" palladium. We are all
stiving to balance speed, color, etc... to make the prints we like to see.
You might try mixing the B&S at 30 to 32 grams to 100ml instead of 26.8.
You should see an increase in speed and contrast. Whether in will
dissolve is another question. At least for users "afraid" to try
something new, (ie making their own or using Brians, Artcraft ferric, or
whatever) they would be using the same material only at a different
concentration.
> The final prints indicated that the Miller F.O. indeed worked.
> The Miller F.O. required at least 20% less exposure than B&S.
> The Miller F.O. also produced a more neutral color and seemed to have a
> tad more contrast than the B&S. Although, the contrast difference may
> be only a result of the shorter exposure.
Is it not true that longer exposure normally gives contrast to the print??
> Both F.O. had excelent depth and substance.
> Both F.O. gave acceptable results. (acceptable to me, critical of
> subtleties)
>
> In conclusion:
> I would recommend either F.O. for the pt/pd process.
>
> However, please keep in mind that I have not tested the longevity of
> Miller's liquid F.O. I have B&S powered F.O. which is seven years old
> and works as good now as it did the first day. I do have some of the
> Miller F.O. sample left over which I plan to keep for a couple years and
> retest.
>
Longevity may be more an issue of how one using and or adbuses their
ferric, getting to warm, exposure to UV light, etc. Perhaps this is
another issue of use such as buying precoated paper?
> I am curious and somewhat concerned as to why the Miller F.O. turned
> dark blue with the addition of PF. I wonder what other material may be
> in the Miller F.O. since Ferric Oxalate will not turn blue with the
> addition of PF. I asked Brian Miller why this was so, but he does not
> know either.
>
> The following is quoted from Brian's response to me on this inquiry:
>
> "I ran the same ferricyanide test on Fred Fosters FeOx a few years back
> & got the same results that you are getting with mine. He couldn't tell
> me why it happened so I just accepted it. My FeOx is a blend of stuff
> made in a few different ways which seems to cause the ferricyanide
> reaction. I suspect that there is some ferrous somewhere in there, but
> not enough to cause fogging. I figured out how to make it this way about
> 7 or 8 years ago & just made it to give me the results I was looking
> for. Eventually others wanted the same results. I also find it to be a
> bit faster, but not more neutral in tone. I find that it also has a
> richer black. I'm not a chemist, so I can't really answer your question,
> but I can assure you that there is nothing funky lurking in there... I
> hope this helps."
>
> I can accept Brian's reason (or lack thereof), except that I do not
> believe that there is any ferrous in Brian's F.O., but rather some other
> material which reacts with Potassium Ferricyanide. It would be a good
> research effort form someone to analyze the contents of the F.O. I do
> not have the time nor equipment.
>
> Hope this information is helpful.
>
> Jeffrey D. Mathias
>
Happy Printing
EJ Neilsen
ejnasn@laplaza.org