I will comment in the text.
At 10:05 AM 3/28/98 -0800, you 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.
Palladium chloride is almost totally insoluble in water. You say you bought
the "galvanic" solution that for the *most part* had the aqua regia
removed. That is most likely where the problem is. Nitric acid is a
powerful oxidizer and is acting like the ammonium dichromate in the Ziatype
print and is surely causing problems -- grain would be the result.
>
>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.
The nitric and hydrochloric are causing your clearing problems along with
other impurities that are likely with this type of solution. If it is for
plating it does not have to be very pure.
>
>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!
That sounds way too low. I haven't measured it in years but I recall it
being apporximately 2.5
>
>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?
Yes Yes. As for the longevity, that is an open matter. Since you will wash
the print, the acid will be gone but there is the possibility that it will
hae damaged the paper thus making it brittle. I had an academic type years
ago communicate with me that he had been observing the results of clearing
with hydrochloric acid and EDTA under an electron microscope and said there
was highly visible damage to the paper fibers in prints cleared with a
standard acid solution. He promised to send some pictures but I never got
them.
>
>3) Would it be possible to raise the pH adding, say, Calcium carbonate or
> Sodium hydroxide and still use the solution?
No. Highly unlikely.
>
>Thanks for any advise you may give
>
>Francesco Curcio
>Milano Italy
>
Bostick & Sullivan
PO Box 16639, Santa Fe
NM 87506
505-474-0890 FAX 505-474-2857
<http://www.bostick-sullivan.com>http://www.bostick-sullivan.com