> Will your test data for palladium prints include details of the parameters under
> which the tests were made. Was the paper sized and with what, what light source
> was used, what was the peak UV output. All these factors can affect the result.
> I ask in the light of a previous academic analysis of papers for gum printing
> with careful representations of the number of steps on a step wedge that each
> paper would take. The test demonstrated that most of the papers used were
> entirely unsuited for the purpose. Had the parameters been more carefully drawn
> in the light of the basic principles of the process, such as absorbancy, PH,
> freedom from contaminants and so on. all the hard work put into the tests would
> have been of greater use.
For my now infamous paper tests for palladium, all papers were tested
as they came from the manufacturer. No additional sizing was used. My
lightsource is 10 24" Voltarc Actinic F20T12/AQA/BP-40W fluorescent
tubes spaced 1/2" apart and at a distance of 8 inches from the
sensitized material. The coating mixture consists of equal quantities
of 27% ferric oxalate (without additives) and palladium chloride
solution (whatever the standard % is) to which I add 1 drop hydrogen
peroxide per 2 ml. For each 4x5 test print 0.5ml of this is applied
with a glass coating rod. Papers with too rough a surface for the
rod were coated with hake brush (in Japanese "hake" means "brush")
using about 50% more solution. Dried with hair drier set on low
setting. Exposure time was 10 minutes at a distance of 8 inches.
Developer used was plain potassium oxalate (no chlorate or
dichromate). Clearing was 3 trays of 4% phosphoric acid for 5 minutes
each followed by 5 minutes in Kodak hypo clearing agent to remove any
residual yellow stain. (For Arches Platine HCA was used for all.)
Then prints were washed 20-30 minutes and air dries on screens.
As for the other parameters Terry mentions, absorbancy varies
somewhat from paper to paper but most were within a fairly narrow
range as estimated by amount of material used for coating. The only
way I know to test paper pH is using the Light Impressions pH pen or
something similar. Unfortunately mine had dried up but I'll get a new
one and see what it says. As for freedom from contaminants, if were
talking of in the paper itself, how can you tell? I can only guess
that some sort of contaminant causes the black spots in Twinrocker
White Feather and probably what looks to me like tiny non-absorbant
fibers in several others. Any suggestions as to how to measure and control
these and any other parameters would be much appreciated. As I've
said before, there are so many variables in the process and in each
practitioner's working conditions that very little is absolute.
> Taking a more empiric approach I would be interested in which papers showed up
> best and under what conditions. What I want from the data is to know is whether
> all your hard work demonstrates whether I can get better results than I already
> get using Fabriano Artistico hot pressed 300 gsm which I mentioned in my note in
> this correspondence on 5 February.
My results show that for my working conditions and methods the papers
that most meet my criteria are Cranes Platinotype and Parchmont,
Arches Platine, Simili Japon, Lenox, and Buxton. However, I began
this whole paper thing to find a substitute for Platinotype since I
needed something larger (longer) than the 23x29" size of that
excellent paper and heavier than Parchmont. That leaves only Platine,
Simili Japon 225gms, and Lenox.
To be continued ....
Keith