salt printing as practise for platinum/palladium

[sanking]

Jorge,

There is no reason to be concerned about questioning my statement that a palladium toned kallitype is physically the same as a straight palladium. I would assume that somebody would question a statement of this type and if I were wrong I would want to know so the discussion is really very useful. However, I still believe I am right in that there is no essential physical difference between these two types of images. However, your comments about completion raise some questions as to whether the replacement of silver by gold, palladium or platinum can b e 100%. But the fact that a palladium toned platinum is visually identical to a straight palladium suggests to me that the percentage of replacement is extremely high, and if it is indeed very high it seems reasonable to believe there is the possibility that it might go to completion.

For what it is worth I agree with both you and Michael that if the replacement is not 100% we should not label a palladium toned kallitype as a palladium.

The formula given in the earlier message is from Grant Haist’s Modern Photographic Processing, Vol. 2, p. 122. Grant Haist was a senior research scientist at Eastman Kodak in Rochester for many years and this book is in my opinion the most authoritative work ever published on photographic processing.

I think you have a good point when you write, "Unless the optical density of gold is much greater than that of silver . . . you would run out of silver way before you have deposited enough gold in those sites to give the same tone" Haist himself mentions that the difference between the amount of gold deposited when gold is in its aurous state, which is about three times as much as deposited in the aurici state, is a result of the two oxidation states of gold. In practice you will indeed find that when a kallitype print is toned to completion with gold the final image is significantly lighter than before toning. With palladium and platinum toning, however, there is no loss of density. To the contrary, there is a slight gain in density.

Platinum and palladium toning of silver gelatin prints was very rarely done in the 20th century and Haist does not indicate how the process of metal replacement takes place. Perhaps someone with experience in metal chemistry can provide guidance on this issue.

[sanking]

Just a thought. How would one test for the presence of silver metal in a print? It strikes me that a test of this test could conclusively answer the question regarding whether or not palladium or platinum can completely replace the silver.

[Michael Mutmansky]

Sandy,

I'm sure there are several destructinve ways to do this, including mass spectroscopy and also possible re-dissolving the metals with an appropriate acid solution (agua regia?) and then a re-reduction of the metals into precipitates or other derivitaves.

I'm nowhere near a chemist, so I wouldn't know how any of this could be done, but Howard or Dick may have some suggestions as to how a procedure may be determined.

I'm sure the people at the Getty have a procedure that will test for silver in a print. I think all we really care about is that there isn't any residual silver left, which may compromise the image longevity.

---Michael

[Jorge Gasteazoro]

Good enough Sandy, I just wanted to make clear there is no "ax to grind" here, only a good natured discussion.

So, a couple of observations.One, if as you say toning a kallitype with pd increases reflection density, then that suggests to me there is some kind of aggregate mechanism where the combined densities of pd and silver are greater than that of a pd or Kallitype print untoned. This suggest that there is some silver left in the toned kallitype print. I guess that if you make a pd print and a toned kallitype from the same negative and took reflection desnsities this could be verified and we can take a step in the right direction. I might even try it myself, I think I still have the chemicals for kallitypes.

Two, a visual comparison is not "proof" that this is in fact what happened, coupled with the increase of density theory, this would actually suggest that there is more of a "plating" mechanism than one of replacement taking place.

Michael made a good guess, if it was me I would not use aqua regia, I would simply use a strong enough solution of nitric acid and then titrate for silver. Why nitric acid? Because silver is less stable than pd, the nitrate ion should be able to oxidize the silver present (if any) bring it into solution and leave the pd in the paper. If the right concentration of nitric acid is choosen, then even before titration there should be an indication of the presence of silver in the print by the appereance of the print. If at the time you soak the print in the nitric acid solution it becomes lighter, then this would suggest some silver has been dissolved resulting in a lower density. Of course further titration would confirm this, as it could be possible to dissolve some of the pd as well.

If I guessed correctly I beleive you work at a university, perhaps the chemistry department is willing to give you a hand on this, it would make an interesting study case for the undergrad students.

[sanking]

Jorge,

Sounds like a soak in nitric acid might be an easy and interesting procedure to check for silver bleaching. What percent solution would you recommend and how long to you think I should soak the print.

BTW, need to correct something I said earlier. The palladium toning results in more contrast, not greater density. This seems to result from a slight clearing of the highlights that takes place during toning.

[Jorge Gasteazoro]

I would say a 5% solution of Nitric acid should do the job. you dont need to soak it for more than 30 to 45 sec, the action should be pretty fast. But you do need to agitate to aid the reaction.

Let me know what you find out...

[Pete Caluori]

Interesting discussion guys. This past APIS, Dr. Dusan Stulnik (I sure hope I spelled his name correctly) gave an interesting presentation on the non-destructive identification process that the Getty Institute has developed. If I recall correctly, it's some type of spectroscopy and it will identify all substances in the print.

Much the same as Dick Sullivan, I suspect that quite a few historical Kallis and even Van Dykes are masquerading as palladium, or platinum/palladium prints. I asked Dr. Stulnik for his thoughts on this and he too suspects this may be the case, but there is no evidence at this point. An insufficient number of prints have been tested to prove this one way, or the other.

The chemical bonds and reactions are well beyond me, but from my work with Van Dykes, I can say that a palladium toned Van Dyke will virtually not bleach in the fixer, whereas a untoned print will "fade" before your eyes. To me that means the silver has either been converted to a new compound that is not affected by thiosulfate, or it's been replaced. Regardsless, I'm a firm believer in being exact in labeling all processes. I don't know how many folks I've talked to that call their prints platinum, when in fact they have 80% palladium and 20% platinum in their prints.

I sure hope we don't get so hung up on platinum and palladium so as to lose sight of the other processes. Kallis, salt prints, albumen, etc. as all are capable of producing beautiful prints, just different and therein lies our goal - beautiful prints.

Regards, Pete

[sanking]

This message was first posted on the alt-photo-process list but I am also putting it here since it is a continuation of this thread.

I ran a silver bleaching test of some palladium toned kallitype with the ferri+bromide Kodak R-14 formula, diluted One Part A + 15 Parts B + 150 Parts Water for one-shot bleaching of four 4X5 test prints.

The four tests themselves were toned for 10 minutes each with different strength toners, ranging from 2.5ml to 10ml of a 20% palladium solution per liter of toner. All of the prints were toned with 10ml of the working toning solution. As you can see, the print with the strongest toner used about 0.1ml of the 20% palladium. By contrast I need about 0.5ml of the 20% solution to make a straight palladium print.

All of the prints were bleached for 10 minutes each, after I determined that this was the time needed to completely bleach out the image of an untoned kallitype. The amount of density lost in bleaching ranged from a lot for the one toned in the weakest toning solution to very little for the one toned in the strongest solution.

Regarding the print that was toned in the strongest toning solution (10ml of a 20% palladium solution per liter of toner), the measured reflective density before bleaching was 1.42, and after bleaching it was 1.36. This means that the palladium in the print, whatever its form, was contributing about 96% of the total density of the print before bleaching, with 4% coming from the silver. This is actually quite a bit higher than I anticipated after hearing of the results of Etienne with other processes. I believe from my data that it would be possible to reach an even higher percentage of total density from palladium by the use of stronger toners and longer toning times, but it does not seem likely to me that a figure of 100% replacement or conversion could be reached.

What I gather from this test is that a palladium-toned kallitype should have great permanence since virtually all of the silver has been either replaced or coated with palladium. However, since a very small percentage of the silver remains in a palladium toned kallitype I would personally not consider it appropriate to call it a palladium, even though for all practical purposes they are *almost* that.

[Jorge Gasteazoro]

I dont konw Sandy, first I have to say I was wrong and there seems to be a pd replacement process that I was not aware of. Of course I researched this after I opened my big mouth so I am having to eat crow now..:-)

I think that the remaining unreplaced silver is due more to a mechanical problem than a chemical one. IOW I think some of the silver is too deep in the paper and the pd cannot reach it to complete the process. I imagine that with some more agitation, or perhaps heating the tonning solution you could get a 100% replacement.

So in the stricktest sense of the word if the toning is not done to completion then perhaps it would be inaccurate to call it a pd print, but I dont know that it would be misleading if the person took care to tone a Kallitype to completion to call it a palladium print.

Mainly I wanted to say you were right, I was wrong and I learned something new.

[Michael Mutmansky]

Jorge,

Don't let him off the hook that easily! I want to know how much of the silver is plated with platinum or palladium. That is really what you were arguing anyway, and the speculation on the alt-photo group was that the plating could be a substantial factor in the resultant image.

At this point the test Sandy has done only confirms that there are some un-plated and un-replaced silver particles in the print that comprises at least a few percentage of the total visible reflectivity.

The next step is to run the same batch with a palladium 'control' so that the actual results can be compared to one that is known to have no silver. Then the bleached tests can have the further tests done that will confirm the presence of plated silver. Since that control should have none, the difference between the two should be readily apparent if plating is occurring.

Sandy, I'm only busting your chops for the sake of the potentially very useful knowledge that you have begun to collect, as I think we are both on the same page about this issue anyway. It's good to see that you have already advanced the level of understanding on this issue, as it appears that there is little data out there regarding what is actually happening in the toning process. Keep up the good work.

---Michael