Re: Palladium

Scott wrote:
> I'm interested in beginning work with palladium printing (speciffically
> Ziatype). I see that Photographer's Formulary lists Palladium II
> Chloride and Sodium Palladium Chloride. Which is the prefered metal salt
> and what would the differences be between the two salts?

The first is PdCl2,
the second Na2PdCl4

The double salts of palladium are usually very hydrophilic, meaning they
like to adsorb water. This can make for difficulties in weighing out
proper amounts. Therefore, it is recommended to buy PdCl2 and whatever
chloride salt is to be used.

This brings up the second point. The type of variation on the PtPd
process to which you refer typically uses the double salt Li2PdCl4. The
lithium salt (LiCl2) is used. Complete directions for weighing and
mixing solutions can be found in my e-guide from the link at the end of
this message. One reason for the use of the lithium salt is that it is
thought to help retain moisture in the coating which is important if
looking to get the more neutral or bluish colors. Although other salts
may be used with various effects. Another reason is that it is thought
that the lithium salt helps with the printing out process. This however
is more of a factor of the sensitizer used, that is ammonium ferric oxalate.

As you may expect the salts are interchangeable as well as the
sensitizers and can even be used in combinations producing various
results. However, only some of the many combinations give full printing
out results.

With lithium especially, note that your ambient relative humidity during
coating and exposure can provide a variety of results. Also be
concerned that ambient temperature plays a part. I have found the best
consistency at temperatures in the low 60s F. Higher temperatures can
produce a variety of problems. Lower temperaturs do not seem to be a
problem until low enough to cause precipitation of the solutions
(something to also be concerned of with saturated solutions.)

-- 
Jeffrey D. Mathias
http://home.att.net/~jeffrey.d.mathias/