Yes, I have solved the black speckelation in my
own work. It was a particular problem with
Cranes Business Card Stock (the one optimized
for Dick Arentz, sold by B&S), Platine, and
other similar thickness and toothed papers. I
noticed that more specks seemed to occur under
hot printing conditions, but usually got specks
anyway (and you know if a speck is going to be
there, it will most likely be in the worst and
most noticeable place).
After some research and talking to a Chemist
with a precious metal manufacturer (Engelhard),
I decided to eliminate sodium from my processing
chemistry. My conclusion came as follows:
Since all other sources of the specks were
eliminated, it had to be what was left (Sherlock
Holmes, sort of). I hypothesized that it had
something to do with the Platinum salt. There
were two scenarios.
ONE: The platinum salt was not pure. Solution:
Find a different manufacturer. Unfortunately at
the time, I was just trying some metal salts
from B&S since they had, at the time, a better
price then Engelhard. This variable confused me
a bit so I decided to stick with Engelhard as
supplier. I remember some discussions with
Richard over the quality of B&S metal salts. At
the time I did not know what the problem was but
I did know that I had eliminated just about
everything. They let me trade a print for some
material in lieu of cash, so all was well.
TWO: Something in the formula was causing the
platinum salt to go bad. Solution: The research
showed that K2PtCl6 was bad and that K2PtCl4
(the desired platinum salt) could be converted
under conditions of heat over 140F, which could
be expedited by the presents of Sodium. So I
eliminated sodium from my formula. The only
source of Sodium was in the palladium salt. So
I modified the formula.
It is interesting to note that I also found the
traditional solutions of metal salts to not be
correct for the solution of Ferric Oxalate I was
using. So I also recalculated the solution
formulas. The traditional solutions have too
little platinum salt and too much palladium
salt. It is another story, but I have made
prints from various formulas and have decided to
use the solutions which gave the best results.
Since the reduction of palladium salt made no
difference, it was OK. The increase in platinum
salt did make some difference, but not when used
as less than 50% of the metal. So I only use
the increased platinum when used alone. Anyway
the formula for the palladium salt is calculated
as follows (using 27% ferric oxalate).
Each Fe2(C2O4)3 will require K2PtCl4 or Na2PdCl4
or K2PdCl4
the molecular weights being: 415.11
294.19 326.42
The standard solution of Ferric Oxalate
(molecular weight 465.82) is 27%.
It follows that the solutions for the metallic
salts be:
24.06% 17.05% 18.92%
Palladium (with Potassium):
From this equation:
K2PdCl4 = 2KCl + PdCl2
are derived these solution percentages:
18.92% 8.64% 10.27%
The modified Pd solution with Potassium:
Palladium PdCl2 5.14 g
Potassium Chloride KCl 4.33 g
H2O 50.0 ml
Weigh out dry chemicals into 2 oz bottle
Add H2O and Shake well.
Place in hot water bath to dissolve.
Intermittently shake. Look at solution in
dropper, it is dissolved when solution looks
clear not cloudy.
One disadvantage with this solution is that it
will not stay dissolved at room temperature. I
place the bottle of solution in a water bath in
a metal roll film tank (the only use I have for
these things now) and place on a coffee warmer
(my only use for this thing too). Works great.
BOTTOM LINE IS: Since using the potassium
formula and eliminating sodium from the coating
solution, I have not had any specks.
Does this mean that my hypothesis might become a
theory? I don't know. I don't even know for
sure why this works. But it does; the specks
are gone.
As a side note: Sometimes the old Strathmore
500 plate finish drawing paper got black
specks. But, those were do to impurities in the
paper and could be located by placing the paper
on a light table to candle. Every piece of
Strathmore paper I use is candled.
Try the formula and let me know if this works
for you.
-- Jeffrey D. Mathias http://home.att.net/~jeffrey.d.mathias/