I am in agreement with Mike Ware that we need to dispense with ferric
oxalate. Chemically it is what is called an "ill defined compound" very
similar to ferric ammonium citrate. It is what is known as a polymer and
can take many different chemical forms. It is also difficult if not
impossible in the manufacturing process to control how it will finally turn
out. The process that I use tends to be more predictable than the
traditional method.
Ferric ammonium oxalate and ferric sodium oxalate were first proposed by
Guiseppe Pizzighelli in the 1880's in the form of a platinum pop process
which has been updated by Ware with his POP process and me with my Ziatype
POP process. I am currently working with some other double oxalates, most
notably ferric lithium oxalate as a substitute for the traditional ferric
oxalate. All of the double oxalates work well with minor differences in
characteristics. They can also be made from a powdered grade ferric oxalate
and with some difficulty, from liquid grades due to the initial solubility
factor of the liquid grades - it is to dilute to begin with.
One of the difficulties of using the double oxalates is if the print is not
fully dry before exposure, you will get a raging print out image.
Jeff is right, many other things can trigger the ferricyanide test. In my
opinion the test is totally unreliable as it is too sensitive. Those old
enough to remember, will recall that in the early 80's we marketed a B&S
ferric oxalate test kit. I discontinued it as it gave so many false
positives that it proved worthless -- well kind of, we sold a ton of ferric
oxalate to folks who didn't need to replace their old stuff. EDTA tends to
trigger false positives. In a word, it's worthless as a test.
Ferric oxalate will always have some ferrous in it and I think it is due in
part to the grand design of the universe. As it ages, it builds up ferrous
and gets faster -- thus the older it gets the faster it gets. (Shucks
fellows, don't you wish!)
Classic B&S help line call: Professor shows up to teach Pt/Pd class. Struts
into first class with negative - "yeah we're going to show these pink eared
bunnies how to make a palladium print!" She coats and dries and exposes.
Print is very weak and contrasty, just some dark streaks. Professor is now
pink and turning a livid red. Two more prints. Same problem. Professor goes
to box and gets some of her trusty coating chemicals she brought from home
and makes a print. Voila! A gorgeous image. Professor calls B&S and starts
raging. Melody manages to calm the situation down.
Two things are happening here. One is that the Professor's ferric oxalate
is 6 months old and is building up ferrous and getting as much as a stop or
two faster. The stuff purchased for the class is fresh. Secondly she is
using fresh developer. Developer that has been used before, will build up
palladium salts and will tend to be slightly faster -- and a whole bunch
faster if the print that is being made is a pure platinum print. Pure pt is
much slower than pure pd, that is if it is not developed in a pd developer
where it will become a mostly pd print.
Ferric oxalate tends to have a mystique all of it's own, but in my mind
mostly undeserved. We have dozens if not hundreds of printers who work with
our powdered grade ferric oxalate and get great results. Most good printers
dope it up in one way or another. Some add peroxide, some edta, some oxalic
acid, some add lead citrate or lead oxalate and most, use it straight out
of the bottle. Most liquid grade work well too, but as Jeff points out the
powder will last almost forever. I have some here that is still good and
has our old lables where the description was put on with a rubber stamp,
this predates my 64k tan cased Osborne CPM computer and Epson mx80 printer
that I subsequently started doing labels with, so I am guessing it was
prior to 1980, putting it somewhere in the 17+ years old. It is still
perfect.
Bottom line. Carl Weese and I are working on a book that will explain a lot
of this information which is coming out of our current research --
hopefully around the first of the year.
Dick Sullivan
At 03:41 PM 8/2/97 -0400, you wrote:
>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).
>
>The first test was to check for the absence of Ferrous Oxalate which may
>be present due to exposure to light or heat or improper manufacturing.
>This also checks if the ferric is changing into ferrous. For this I use
>Potassium Ferricyanide (PF). By adding one crystal of PF to 10 drops of
>Ferric Oxalate no change should be noticed. Then upon exposure to
>printing light (conversion to Ferrous) the solution should turn dark
>indigo blue.
>
>At the start the Miller and the B&S were about the same yellow color
>with the Miller a tiny bit darker. There was slight, but no real green
>color to either.
>
>When I added the PF, Miller's immediately turned dark blue. The B&S had
>no change. The change of color to dark blue should be an indicator that
>the F.O. has been exposed or has gone bad. However, I proceeded with
>the next test.
>
>The second test was to check for fogging and clearing. A standard pt/pd
>coating mixture is prepared and coated onto a paper that is known to
>clear well. Pencil dots applied after drying indicate the edge of the
>coating. This is done for each F.O. Both are then put through
>processing with no exposure.
>
>Both prints cleared completely meaning that the Miller F.O. had not been
>fogged as indicated by the first test.
>
>The third test was to make a print for a negative I have reserved for
>these tests. It has a full range of values, large areas of solid and
>continuos tones, and areas of detailed lines and texture. This 4x5
>negative has been printed onto many paper types and chemical
>combinations all stored for reference.
>
>The prints were made on Cranes Platinotype paper (Cranes business card
>stock optimized by Dick Arentz)(available from B&S) with a coating
>formula of 6 drops F.O.; 1 drop 1/4% potassium chlorate; 4 drops
>Palladium salt; 2 drops Platinum salt. Exposure was given by exposing
>several coatings at different times. All processing was:
>development/enhance in potassium oxalate; pre clear in tap water; clear
>in phosphoric acid; wash in tap water.
>
>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.
>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.
>
>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
>
>
>
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