By "spectra analysis" do you mean X-ray fluorescence spectroscopy that
I suggested here a few years back? If so, I'm glad to know you found
someone to help you on this issue. This method will give you reliable
figures for silver-to-palladium ratio, for example, as you asked at
that time. An additional consideration you want to make is what degree
of conversion is sufficient for your material and procedure to provide
adequate image protection. The most standard procedure for this is
peroxide fuming test as outlined in ISO/ANSI standard.
The toning reaction of your solution relies on the difference in
ionization of two metals. In other words, the toning reaction is an
electrochemical reaction where Ag0 is oxidized (anode reaction) and Pd
(2+) is reduced (cathode rxn). There may be neat tricks in making the
reaction faster, but this would involve close literature research and
some experimentation than what I can provide here.
One possible direction is to change the form of palladium. For
example, you might want to look into other ligands for palladium. I'd
definitely consider ammonia or organic amine compounds. I'd also
consider sulfur compounds like thiourea, thiocyanate and various
thioether compounds. These agents may also increase the activity of
the anode reaction.
Another possible direction, if you don't care about remaining silver,
but care about the amount of palladium being plated out, you could
adjust the redox potential, etc. of the bath to accelerate the toning
process. This is basically a problem of formulating a physical
developer which deposits palladium instead of silver. (It could also
be viewed as a palladium intensifier.)
Unfortunatelly for any of the above points, I can't give you any more
specifics without doing further research.
In toning silver-gelatin image, one large factor affecting the rate of
toning is the surface-to-volume ratio of the grains. The grains with
greater s/v ratio will tone faster and to a higher degree, if other
factors are equal. The ratio varies greatly depending on the developer
formula as well as exposure, even with the same emulsion. This may not
be a factor that's easily manipulatable in kallitype but you might
want to keep it in mind.
Ryuji
Received on Tue Nov 15 08:03:45 2005
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