Severe staining when toning a Van Dyke Brown print in gold thiourea toner ...

[koraks]

My prints that I processed haphazardly have faded and irreversibly degraded within a few years. Perhaps yours fare better!

 

[nmp]

Just out of curiosity, do you have any background in chemistry ? I’m asking because your answers are detailed and very useful !

OK so now that you are trying to out me....

I am not a chemist chemist, as I like to say but with a BS in ChemE, so perhaps a poor man's chemist. My graduate work was in materials science with polymer emphasis so learnt some polymer organic chemistry as well but mostly focused on the physical aspects as they relate to chemistry/molecular structure. Not much inorganic chemistry which much of what we do in alternative processes falls under. Later I practiced all that in the semiconductor industry. I have left all that behind for more than a couple of decades now. So a lot of it is rusty but does come in handy from time to time. Nowadays if you have forgotten something, internet is a great tool to refresh it up.

So yeah, I do sound like I have background in chemistry - enough to get me in trouble. I am glad some of that stuff is helpful.

:Niranjan.

P.S. Looks like a great print by the way. You can share the image on the HCWP showcase thread.

 

[largo]

My prints that I processed haphazardly have faded and irreversibly degraded within a few years. Perhaps yours fare better!

Hi @koraks !

Quoting Dick Stevens in his book "Making Kallitypes A definitive guide", chapter "Clearing & Fixing Kallitype II prints", pages 156-... :

Fixing kallitypes serves the same purpose and follows much the same procedure as fixing conventional silver prints, but there are notable differences. In kallitype printing, the silver image is formed directly on the fiber of the paper rather than in a gelatin or other colloid medium. This makes the task of dissolving the silver salts in kallitype prints easier to accomplish, since these salts are more accessible. But the accessibility of the silver has some disadvantages. Since there is no medium on the surface of the print to protect the fine-grained silver that constitutes the image, kallitypes are vulnerable to chemical attack, both during and after processing. For this reason, care must be taken to avoid strong concentrations of hypo lest the image suffer serious bleaching.​

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A second consideration when fixing kallitypes is that the silver salt to be removed is silver nitrate, a readily soluble salt. The silver salts used in conventional photographic sensitizers made with the silver halogens (bromine, iodine, and chlorine), are quite insoluble and require the presence of an ample supply of fixer to dissolve them. The use of soluble silver salt for kallitypes permits abbreviated fixing times and weak concentrations of thiosulfate.​

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A third consideration is that the kallitype developer and clearing baths do not carry over chemicals that attack the fixing bath, as do certain baths in conventional silver print processing. Thus, fixing kallitype prints poses few problems. Since the non-image-forming silver that must be removed is soluble and quite accessible, a relatively weak concentration of fixing solution will suffice and the fixing can be accomplished in a relatively short period of time.​

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There is one problem that arises when fixing kallitype prints. Ideally, fixers dissolve the non-image-forming silver salt and have no effect on the image-forming silver, but this goal is not always attained with the kallitype process. The silver that forms the kallitype image is vulnerable to chemical attack during processing and is particularly susceptible to attack by the fixer. If the fixer is too strong or is applied for too long a period, it will bleach the highlights of the kallitype image. Fixer concentration and timing must be strictly controlled lest the delicate prints lose image quality.​

Then there are a couple of paragraphs about the history of fixing kallitypes...

Then follows paragraphs about the recommended fixing time :

In general, kallitype paper fixes more rapidly than negatives, and plain paper prints fix more rapidly than do prints coated with colloids. This is because the silver salts that must be dissolved are directly accessible (rather than in a medium that must be permeated). In addition, kallitype papers fix more readily than chloride or bromide papers because the silver salt used, silver nitrate, is more soluble. For these reasons, fixing times of 5 minutes total are not unreasonable when fresh baths compounded in 5% concentrations are used. The prints should be well agitated, and there should be only one or two prints in the fixing bath at any given time. Even shorter fixing times may be possible when prints are well agitated and maintained in contact with the hypo solution throughout the fixing time.​

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L.A. Mannheim, in The Focal Encyclopedia of Photography, reports that the time necessary to completely fix a chloride contact print in fresh fixer is about 1 minute. As the bath approaches exhaustion, the time of fixing lengthens, up to 10 minutes. The implication of these times for fixing plain paper prints is obvious: Fixing times for kallitypes can be as short as 5 minutes in a fresh bath.​

Dick Stevens, who has extensively studied the history and practice of kallitype and wrote a 250 pages book on this topic, recommends fixing kallitypes in a 5% hypo bath (slightly alkaline) for 4 to 5 minutes. Is he actually totally wrong?

Now regarding your older kallitype prints that turned yellow in the lightest areas and/or faded over time (loss of density) : Could the yellowing and fading be caused by residual ferric ions left on the paper or by hydrolysis of the ferric through the use of a developer that has become basic or a first clearing bath that is not acidic enough ? Was disodium EDTA used in the first clearing bath ? You pointed out the fixing time being too short or the fixer too weak, but can you rule out an insufficient clearing (or even maybe an exhausted developer ?) ?

I'm not questioning your observations, but as I'm reading radically opposed opinions about the fixing of iron-silver prints, and as I would a priori tend to trust Mr Stevens, now I don't know who to trust any more !

N.B. The altphotolist thread that Niranjan mentionned is very interesting, but about fixing salted paper print, so about removing unexposed silver halides (chloride), not silver nitrate...

P.S. : Do you think I could simulate the "aging" of my prints by exposing them to UV in my UV unit and see if I can see any signs of bad fixing ? Also, in "Professional Printing with Kodak Photographic Papers", 3d ed. (Rochester, N. Y.: Eastman Kodak, 1963), pp. 30-31, there is a procedure for testing whether or not a print was sufficiently fixed, using a solution of sodium sulfide...

 

[nmp]

P.S. : Do you think I could simulate the "aging" of my prints by exposing them to UV in my UV unit and see if I can see any signs of bad fixing ? Also, in "Professional Printing with Kodak Photographic Papers", 3d ed. (Rochester, N. Y.: Eastman Kodak, 1963), pp. 30-31, there is a procedure for testing whether or not a print was sufficiently fixed, using a solution of sodium sulfide...

I did just that but using the Sun for my salt prints as I explained in this post for fixer efficacy. You can also check out the thread on altproclist that I linked. I also did a quantitative study with residual halide test, may be I can dig up later to share. Again this was for salt prints, but testing own process is a good idea. One person's 5 minutes may very well be another's 15 minutes.

:Niranjan

 

[nmp]

N.B. The altphotolist thread that Niranjan mentionned is very interesting, but about fixing salted paper print, so about removing unexposed silver halides (chloride), not silver nitrate...

I have thought about that too and I would be surprised at that time in the process there is any soluble silver nitrate present in the paper. Part of it would have come out as the print first goes in the water and the rest would be converted to halides, and other salts - some of which will float away and the rest stay in the paper. Finally, there will be some new silver chloride created from the replacement toning with Au chloride. So I would say by the time the fixer comes in silver is in the form of insoluble salts.

:Niranjan.

 

[koraks]

Now regarding your older kallitype prints

Not kallitypes. Van Dykes. Sorry if this wasn't clear, although I did mention it explicitly.
So no developer. Wash with water acidified with citric acid, which acts also as a chelating agent, although undoubtedly far less effectively so than EDTA or PDTA. Fixed with plain hypo. I relied mostly on this text by Sandy King: https://unblinkingeye.com/Articles/GTV/gtv.html

Note that King also mentions (possibly relying on Stevens as well) the allegedly brief required fixing times:

The silver nitrate that is not used in image formation is highly soluble so in theory Vandyke prints need much less fixing than silver gelatin prints.

So both Stevens and King purport that it's silver nitrate that needs to be fixed out. I find that riddling, because silver nitrate doesn't require fixing. Both gentlemen also mention that the salt is highly soluble, so why fix such prints to begin with? Apparently, practice doesn't want to conform so nicely to theory, and something else is going on. In my simple mind, the silver ions either complex with ferric or ferrous salts (e.g. silver ferrocyanide), and/or with chloride, which is likely present in the paper base itself or as part of any of the water used in making up the sensitizer, wash bath etc. Otherwise, unfixed Van Dyke's, kallitypes etc. would remain perfectly fine, but I guess we all know (or at least believe) that they don't.

This then leaves the question how much fixing is enough. I'd like to highlight the fact that I responded to your earlier remark about fixing for 2 minutes in plain hypo (step #8 in your initial process description, post #1), apparently a 3% solution according to post #8, which I found (and still do) very brief. You're now quoting Stevens and paraphrasing his proposed fixing time as

in a 5% hypo bath (slightly alkaline) for 4 to 5 minutes

That's quite a difference, both in concentration and time. I'd like to add that King in the link I provided above suggests something along similar lines as Stevens does:

Fix for three minutes in a 5% sodium thiosulfate solution. For maximum archival quality, use two separate fixing baths and fix for two minutes in each, with a rinse of about one minute in running water between the first and second bath. The second bath should always be fresh fixer.

Both of their recommendations constitute significantly more thorough fixing than what you were doing.

As to the fixing of silver chloride prints: after Van Dyke's, I moved to salted paper prints and have done very extensive trialing with those, also with gold toning before fixing. My experience with salted paper prints (i.e. silver chloride on a plain paper base, no colloids involved) fix out with rather extreme difficulty. The fixing is perhaps 99% done in the first minute or perhaps quicker, but the remaining 1% appears to be very, very difficult to get out. Why this is, I don't know. I always understood that in a plain paper base, salts tend to embed quite firmly between and inside paper fibers, which you know is a very tightly woven mesh (a bit like a colloid layer, just at a different scale). It may also have something to do with silver complexes other than silver chloride somehow forming during processing that are even more difficult to fix than silver chloride. Either way, if silver chloride is part of the package of silver salts that needs to be fixed out of a kallitype or Van Dyke print (you know, with practice once again failing to conform to theory as we'd like to), then I don't see how the difficult to fix tail end of a salt print would be all that different from a kallitype.

I do understand the balancing act between degrading density due to overfixing in silver-based alt. process prints, but given the tricky situation when it comes to 'archival' processing, I'd just want to warn against erring to the side of underfixing.

 

[revdoc]

One thing to bear in mind (in case it hasn't come up earlier) is that silver nitrate will stain badly if it comes into contact with fixer. Residual fixer tests like Kodak HT-2 use silver nitrate in exactly this way. Since fixing doesn't stain Kallitypes and VDBs, silver nitrate probably isn't the issue.

I always assumed that traces amounts of chloride in tap water will convert some silver nitrate to silver chloride, as will some toners. E.g., gold chloride will convert silver to silver chloride. In some cases, it could also be silver citrate (though I don't know whether fixer will remove that compound).