Re: Toning kallitypes and vandykes

Ryuji,

Yes, by specrta analysis I do mean X-Ray fluorescence spectroscopy. I
met someone from the Getty who was interested in the project because
it has implications for his own conservation work with toned prints
from the 19th and 20 centuries. So I prepared some samples which he
tested and based on the results we hope to modify the toning
procedure in an effort to make it more efficient. The efficiency, as
measured by the replacement of silver with palladium, can not be
evaluated visually at since 2.5 minutes of toning gives the same look
as 20 minutes of toning, but there is a big difference when measured
with X-Ray spectroscopy.

Thank you for your suggestions about possible directions for
experimentation to speed up the process. I also thank you for the
suggestion about peroxide fuming. The most likely course I will
follow at this time is attempt to increase the activity of the anode
reaction by modifying the toning formula to include thiourea and/or
thocyanate, and/or make changes in pH of the working solution.

Sandy

>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 10:02:59 2005