Long term stability of Pt/Pd prints on paper

Marco B submitted a new resource:

(there was a url link here which no longer exists) - Long term stability of Pt/Pd prints on paper

NOTE: This is a copy of the last concluding post in (there was a url link here which no longer exists) here on APUG. I thought it wise to add it here as well, for better accessibility to others.

*** CONCLUSIONS: ***

- Despite the noble metals themselves being virtually indestructible (only concentrated hydrochloric or nitric acid will dissolve them), both true...

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(there was a url link here which no longer exists)

Nice. Thanks.

I concur with Mr Cardwell
very helpful informatin

df cardwell said:

Nice. Thanks.

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Thank you, Marko.

May I copy this and use it in workshops and give it to our university students? (with a credit line to you, of course.)

Vaughn

Vaughn said:

Thank you, Marko.

May I copy this and use it in workshops and give it to our university students? (with a credit line to you, of course.)

Vaughn

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Yes, no problem, it is all publicly available knowledge and articles I refer to. You might want to credit Mike Ware for his kind remarks as well, although I think I have already done that more or less properly in here.

Also remember that most of the discussed issues, are equally valid for any of the other Iron based process, like VanDyke Brown.

Important CORRECTIONS to my conclusions

Hi all,

Mike Ware was kind enough to give some remarks on my last set of conclusions.

Especially noteworthy of course the remark about papers having an alkaline CalciumCarbonate buffer. While they may be good from a point of longevity of the paper base, as Mike points out, they are "disastrous" for the iron sensitizer itself, making it difficult if impossible to get good prints at all in the iron based processes, so this topic should be skipped.

Of course there may be a case for an alkaline Calcium(Bi-?)carbonate bath after the print has been completely processed to restore a slightly alkaline buffer (as is mentioned on the linked Iron Corrosion website), but that is a different story...

Upon my request, he has also given some more information on the possible use of SodiumDithionite/EDTA bath and how to employ it.

Many thanks to Mike Ware for these further comments.

*** Mike Ware's comments ***

Sodium dithionite becomes a much more powerful reducing agent in alkaline solution.
Sodium dithionite is unstable in acidic solution, decomposing to thiosulphate and bisulphite.
The complex formation between Fe(II) and EDTA is a maximum in alkali (~pH 10).

So to get the best reduction of Fe(III) to Fe(II) and removal of Fe(II) as chelate, one must therefore use alkaline solution.
That means, effectively, using Na4EDTA not Na2EDTA.
Rees and Gent started by using Na2EDTA (possibly, they didn't have any Na4EDTA) and adjusted the pH by addition of NaOH. They found rather little iron-removal action at pH 6.5 and much more at pH 8.5. (I won't go into the additional conservation reasons why they tried the lower pH).

My present recommendation is simple:

A solution that is 2.5% in Sodium Dithionite and 2.5% in Tetrasodium EDTA, which should result in a suitable pH around 8.5, with no need for adjustment.
Treat for half to one hour. Stronger solutions could be used, but this is economic and effective, and should be frequently changed, if one is treating a lot of work.

If you are editing your article, could I just point out a couple of things?

The word you need in the intro paragraph is "threat" not "thread".

In 1) NOTE: the absence of catalytic activity with palladium is NOT PROVEN so far as I know. I have just not seen any evidence of it, that is all. Absence of evidence is not evidence of absence.

In -Print 100% Palladium prints : the recommendation of calcium carbonate containing papers is disastrous for all the iron-based processes because it promotes hydrolysis of the iron(III) photosensitizer. This advice completely defeats the original purpose! If you practiced any of these processes, you would know to pre-treat your paper with acid to DESTROY any calcium carbonate. Talk to Loris about this. I only use papers guaranteed not to contain calcium carbonate.

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LATEST VERSION OF ARTICLE

Hi all,

I have now updated and rewritten my set of conclusions on the longevity of Platinum / Palladium prints. It is now a more accessible and complete "article", with a proper introduction and a few more pieces of background.

There have been a number of significant changes, and I therefore consider the above posts OBSOLETE.

Please download the latest version that I attached here if you would like to read it.

Marco

Excellent resource. Thanks!

Marco, I'm getting ready to learn to print pt/pd and other methods; reading things like this let me know that there is a lot more for me to learn. It's interesting though. I can't say I have absorbed it by any means, but will be something I reference again, and again. Thanks much.