On Sat, 28 Mar 1998, Francesco Curcio wrote:
> Some time ago I decided to try Palladium printing with Dick Sullivan's
> recipe for Ziatype.
> Looking for Palladium chloride (PdCl2) in Italy, I found it in two different
> forms: as a 10% solution made for galvanic use by goldsmiths, reasonably priced (!)
> at about $500 for 1 liter (=100g of PdCl2), or as an analitical grade
> chemical (solid salt) at almost ten times that cost.
> I bought the galvanic solution and asked the guy how he manufactured it.
> He said the pure metal was dissolved in Aqua Regia (the mix of
> Hydrochloric and Nitric acid that attacks noble metals),
> then the acids were extracted (?) for the most part from the solution.
>
> I use 23 ml of it to mix 25 ml of my "B" Ziatype solution (palladium
> chloride+lithium chloride) and it seems to work, but with some trouble.
> I get deep cold blacks on most papers I use, but never a really smooth
> pale gray, my skies are often uneven and grainy. I also have a long
> (an hour at least) clearing process to carry on, alternating citric acid
> and sodium sulfite baths, to get rid of a stubborn yellow stain.
>
> Yesterday I checked the pH of the Palladium chloride solution I bought,
> and I was astonished when I read 0.3-0.4. I know that a Palladium
> chloride salt can only be dissolved in a slightly acid solution,
> but this looks like pure nitric or hydrochloric acid!
>
> Now the questions, if the chemically knowledgeable members of this list
> can help:
> 1) What should be the normal pH of a 10% Palladium chloride solution
> intended for palladium printing?
>
> 2) Could such a low pH have caused the grain and clearing problems I am
> experiencing and be dangerous for the print longevity?
>
> 3) Would it be possible to raise the pH adding, say, Calcium carbonate or
> Sodium hydroxide and still use the solution?
>
> Thanks for any advise you may give
>
> Francesco Curcio
> Milano Italy
>
>