Jeffrey D. Mathias (jeffrey.d.mathias@worldnet.att.net)
Fri, 07 May 1999 13:28:14 -0400
Some thoughts and suggestions on the Ziatype variation.
I have been trying the Ziatype materials and have to agree that they
will provide some unique results and some unique control methods, but
the more I use them, the more it just seems to be the Pt/Pd process.
The Ziatype is nothing more than a variation on the platinum/palladium
process. I think it is critical to keep in mind that the substitution
of the salt ions (Li and NH4) does not change the basic character of the
process to place Pt or Pd into the paper. The chemical reactions are
quite similar as well. Even that with these materials the image prints
out fully during exposure (POP), the basic character has not changed. I
do hope that any beginner to the Ziatype is not fooled into thinking
that this is not the platinum/palladium process. I also hope that those
currently working with the Pt/Pd process will investigate some of the
contributions the Ziatype materials bring to this process.
I am sure there are numerous variations that can be brought into the
Pt/Pd process. It would be a terrible setback to go back to the days of
patent wars and top secret formulas. In these times of the Internet,
philosophies have changed; what was once hoarded as privileged
information is now general knowledge for the masses. (HA! You can't
call me a "commie" ‘cause the wall is down.)
Yes indeed, I certainly offer tribute to Richard Sullivan and Carl Weese
for their hard work to bring the Zia variations to fruition (as well as
any others I am unaware of).
Although the Zia formula as published does work quite well, I have found
some room for improvement. I have found that not enough palladium has
be included in the published formula. I offer the modified formula
below, but will first describe some noted observations.
I used Cran's Parchment Business Card Stock (Lot No. 5302) (or called
"platinotype")
with ambient temperature at 70F and relative humidity at 50-55 %
chemistry for 8x10 was 24 drops sensitizer, 1 drop contrast agent, 24
drops metal salt
coating by brush
drying with ambient temperature blow dryer
exposing 4 to 5 minutes under artificial lamps (see guide for lamp and
arraignment)
a full minute in water (all "water" is 0.5 micron filtered tap water)
clearing was with Phosphoric acid (2oz. 85% reagent grade in 1 gallon
water)
By comparing prints from the modified formula with prints from the
published formula, I have found the following:
+ a slight increase in contrast
+ a slight increase in speed (maybe 10 - 12 %)
+ a tendency for deeper darks (or as some may say: better D-max.
However I do not use a densitometer and only am concerned in what I
see.)
+ a slightly more neutral color
+ a more solid and uniform dark (This is determined by looking at fully
exposed areas (brush marks) while the print is backlit with a bright
light or the sun.)
+ a bit more substance to the tones
As I have optimized my chemicals for the traditional process, I found
none of the above to be unexpected or out of line as possibilities for
the increase of Pd.
Now, don't misunderstand, the published Zia formula makes a pretty good
print.
It's just when I put the two side by side my preference is going to be
the modified formula. For me, I'm finding enough difference to justify
the additional expense of the additional palladium.
I do plan to run these tests of some other papers and to do some further
optimization of the chemistry, but I feel that the results thus far are
significant enough to bring to the attention of those using Zia
variations.
I'll plan on taking prints to APIS in July.
++++++
For the solution of Lithium Palladium Chloride I have calculated the
modified formula as follows.
For the Ziatype variation, Ferric Ammonium Oxalate is used as the
sensitizer with a basic reaction as follows:
(NH4)3Fe2(C2O4)3 = 6Fe(C2O4) + 3(C2O4) + NH4 (or this is attached to
something)
The basic Pt/Pd process reaction with Lithium substituted is:
6Fe(C2O4) + 3Li2PdCl4 = 2Fe2(C2O4)3 + 2(FeCl3) + 6LiCl + 3Pd
To balance this, each (NH4)3Fe2(C2O4)3 will require three Li2PdCl4
Looking up the molecular weights of the ingredients:
FW of (NH4)3Fe2(C2O4)3 is 1415.50
FW of Li2PdCl4 is 262.09 (three of them being (786.27)
FW of LiCl is 42.39
FW of PdCl2 is 177.31
If the (NH4)3Fe2(C2O4)3 is mixed at 40.00 g/100ml (assumed to be fully
saturated),
it follows that the Li2PdCl4 should be mixed at 22.23 g/100ml.
(786.27/1414.50)*40.00 = 22.23
Now, Li2PdCl4 = 2LiCl + PdCl2
which if the Li2PdCl4 is a solution of 22.23%, then
LiCl is a solution of 7.19% and
PdCl2 is a solution of 15.04%
(2*(42.39)/262.09)*22.23 = 7.19
(177.31/262.09)*22.23 = 15.04
This means that the formula should be:
7.19 g LiCl
15.04 g PdCl2
100 ml H2O
or
1.80 g LiCl
3.76 g PdCl2
25 ml H2O
However, the published formula is:
1.7 g LiCl
2.3 g PdCl2
25 ml H2O
Note the primary difference is in the amount of PdCl. It certainly
indicates that about a third of the LiCl won't have any PdCl2 to combine
with. As there is a significant difference in the amount of palladium
used, I would suspect that this would show in the print. And indeed it
does manifest itself in the print as the experiment above has shown.
My recommendation is to use the modified formula which has more PdCl2.
It certainly doesn't make sense to have unused Lithium anyway.
As another thought, and to check the strength of the Ammonium Ferric
Oxalate (AFO), more Li2PdCl4 can be added until no changes in the print
are detected. Or the amount of Li2PdCl4 can be reduced until such point
just before any changed is noticed. If for some reason the AFO is
weaker then expected, this can save some costs. Of course the strategy
is to get the AFO as strong as possible which will depend on the ambient
temperature and pressure. For practicality and use under variable
conditions a slightly weaker AFO makes sense. I have found no problem
with the published formula for AFO which was probably optimized at the
higher elevation (lower pressure) of Santa Fe.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/
This archive was generated by hypermail 2.0b3 on Thu Oct 28 1999 - 21:39:33