Metallic stains on sepia toned prints

Discussion in 'B&W: Film, Paper, Chemistry' started by Marco B, Sep 14, 2007.

  1. Marco B

    Marco B Member

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    Hi all,

    Lately, I have tried to sepia tone a number of liquid emulsion prints (Rollie Black Magic VC). The toner I used is Amaloco T-10 Sepiton, a dutch product of which I am not to sure others know about or if it's sold outside the Netherlands. Unfortunately, the exact contents of this toner is not mentioned on the package. However, it is a two bath system, and it does mention ferricyanide and sodiumhydroxide for the first and second bath respectively. Based on some research I've done on the internet, I know suspect, or almost know for sure, that it is a thiourea based sepia toner, since the other two types of sepia toner either are not odourless and single bath (sodium sulphide based sepia toners), or can not be combined with any alkaline solution like the sodium hydroxide in the second bath, since that would destroy it (metal ferricyanide toners - copper based for sepia). So it's most likely a thiourea based toner.

    Anyway, the problem I've seen turning up is that metalic / silvery stains appear in the *most dense/dark parts* of the sepia toned prints, so those parts of the original photo that had the deepest blacks. Actually, although I'm pretty sure I've stayed below the stated capacity of the toner (in terms of square meters), I am suspecting I may simply have exhausted the toning bath (the second sodium hydroxide / thiourea bath). Toning times were already rising, and I may simply not have fully toned all bleached silver. Many of my prints are also very dark, so requiring a lot of the toning bath...

    Is this indeed possible??? Or am I talking complete nonsense here? Does untoned, but bleached silver, turn into a visible metalic layer on sepia toned images when the toning bath is exhausted? And if not, does anyone know the real cause of these metalic / silvery stains?

    Thanks for any info!

    Marco
     
  2. Marco B

    Marco B Member

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    No one?... I guess I have possible answered the question myself, but it would be nice to have some confirmation of someone with more experience in sepia toning...

    With "metallic" by the way, I mean that these parts also look very shiny / reflective, compared to the rest of the print which has a matte surface. This is especially apparent when I turn the print around relative to a fixed light source. I see a kind of metallic surface popping up than.
     
  3. jim appleyard

    jim appleyard Member

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    Are you toning in metal trays? I don't know if this is the cuase of your problem, but many toner directions will tell you not to tone in metal trays; at least not in metal trays where the paint is chipped.

    I have always used plastic trays for toning.
     
  4. Bob F.

    Bob F. Member

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    I have seen this three or four times and always in the same batch of prints but have no idea of its cause. I find that when I see this in the toner, rubbing the effected area will usually remove the problem (use gloves or a cotton-bud etc as thiourea is reportedly carcinogenic, but I don't know to what degree by absorption).

    I'm pretty sure neither baths were exhausted so I'm wondering if it is insufficient washing causing a carryover from the fixer or carryover of the bleach to the toner. Both seem unlikely as I'm pretty careful of both, but I don't rule either out completely...

    I use plastic trays exclusively.

    'Tis a mystery to me...

    Bob.
     
  5. Marco B

    Marco B Member

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    Hi Jim,

    No, I use plastic trays. The only metal is the stainless steel from the tongs, but these have rubber tips and the metal does not seem to have been corroded in any way by the baths.

    I still suspect incomplete toning by the second sodiumhydroxide / thiourea bath, leaving bleached silver in the image. I am thinking of a test by throwing the affected prints back into fresh bleach and toner baths. If it is indeed a layer of metallic silver, I suspect I should be able to bleach and tone it again.

    Maybe it would be good to fix toned prints as well using a normal fixing bath?? This should get rid of any left over bleached silver, if I have understood some other stuff I have lately read on the internet (not specific to toning by the way).

    Anyone doing this after (sepia) toning???

    Thanks Bob for your response, good to know others have had similar issues. I will let you know what my test results are...
     
  6. Dave Miller

    Dave Miller Member

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    I have experianced similar effects which I too think are the result of toner exhaustion. I now follow Tim Rudman's advice, and refix after any toning that involves a bleaching stage in order to remove any unfixed silver halides left.
     
  7. tim rudman

    tim rudman Member

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    Hi Marco
    Bob mailed me and asked me to chime in. I'm on the road right now shooting for a few more weeks and so rely on WiFi when it is available - or not.
    It would be interesting to see these. Copper does this easily but I haven't seen it with Thiourea toners. Thiourea sepia often leaves a white deposit which dissolved in 3% acetic acid or simply some dilute stop bath, but it doesn't look metallic (to my eye).
    Fixing after incomplete toning would be wise, but expect some loss of tone - and why tone incompletely? better to control at the bleach stage and tone fully.
    Perhaps you can get the toner ingredients from the maker? They might respond, but anyway they should at least have a data sheet (MSDS or hazard substance list etc should be available for users)
    regards
    Tim
     
  8. Marco B

    Marco B Member

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    Hi Tim,

    Thanks for joining in, and thanks to Bob for contacting you. Considering the number of references to you on APUG, and your book, you seem to be one of major experts here on APUG...:tongue:

    Sorry for the late response by the way, my "online" status of the past week was a bit fudged to say the least, as my computer was down but APUG doesn't automatically log you out...

    I've now done some further research, by reading some articles on the internet, and a bit of experimentation.

    First of: I've done the test to try to re-tone the image with fresh toner solution. Both the bleach and toning baths failed to have any effect at all at the staining. So "metalic" silver is almost out of the question.

    Well, reading some more stuff about the workings of (sepia) toners, silly me to even think this was reduced silver. For the silver cation to be reduced to metalic silver, would require at least some reducer / electron donor. Bleach has just the opposite effect, oxidizing the Ag to Ag+ in the form of most likely AgBr, silverbromide, if the bleaching bath has potassiumbromide in it as well (as with most of the sepia toners according to what i've read...). Else, in the absence of bromide, a silverferrocyanide deposit would be formed.
    The toning bath subsequently doesn't do a reduction either on the silver, it merely bounds the Ag+ cation to sulphur, in the process destroying the intermediate silverbromide and resulting in the stable Ag2S component, which is the end result of the toning.

    So, what next? :confused:

    Reading through all the stuff, and again having a close look at my stained pictures, I now have a crazy idea I would like your opinion about. To recap my observations (and see the screenshot I now included!):

    - Staining is almost exclusively limited to the highest density / black areas of the original print
    - Staining starts when the bath is almost exhausted, with long toning times in the second toning bath
    - I have now also been able to confirm Bob's observation: Initially, I thought the stains appeared *after* having left the toning bath (thiourea / natriumhydroxide), but this isn't true. As Bob observed, I've now seen in a used toning bath the *temporary* formation of these stains, that disappeared with some more agitation of the bath.
    - As another new observation, the stains do not only appear more reflective / metalic, but might be "bleu-ish" as well.

    So, here's my crazy idea:

    Could the stains actually be "prussian blue", ferriferrocyanide deposit, as formed in blue toners and the cyanotype process? :confused:

    I know it sounds crazy, because metal-ferrocyanide compounds are supposed to be highly unstable in alkaline environments. However, just looking at the chemical components available in the solutions, there is not much choice, just potassium, sodium, silver and iron are available as the cations to form any kind of stable deposit with the ferrocyanide anion. Ferriferrocyanide deposit is bleu, and might explain the bleu-ish tint of the staining. In addition, it would also explain why some more agitation or "rubbing" as Bob suggested, removes the stains, as this probably helps the weakened alkaline solution to break down the stains...

    Maybe that in exhausted toning bath, and especially in the high density silverbromide areas of the bleached prints, a specific "micro environment" can exist that IS favorable of the formation of prussian blue, despite it's vulnerability to alkaline environments. Of course, with the toning bath almost exhausted, the amount of harmful hydroxide anions is likely to be a lot lower...

    Just leaves the big question, why dumping the stained print back in the alkaline toning bath, doesn't remove the stains either. Well, reading all the stuff, I know also now that the chemistry of all these reactions, and the products they form, can actually be quite involved, and some forms of prussian blue are more stable than others, as we've been thoroughly discussing in this thread:

    http://www.apug.org/forums/forum42/41822-cyanotype-color-change-w-sodium-bisulfite-whats-going.html

    The only other option I see, is some deposit of selenium, caused by contamination. Admittedly, I still need to buy some extra trays, but I've only toned once with selenium, and all the initially toned images, using the fresh toner, came out OK before the staining started (and the selenium toning was NOT in between these sessions, but well before that). Seems highly unlikely and besides, why a "reversible" staining than? and only some of darkest parts affected?... and it would need a "major" contamination of the trays causing so much staining I guesse... I rinse them well after usage...

    It all doesn't make much sense :sad:

    Well, interesting to hear what all of you think!... :tongue:

    Attachement showing stains:
    [​IMG]
     
  9. tim rudman

    tim rudman Member

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    Prussian Blue is not a likely cause for this Marco and in any case, in the photographic media, it is notoriously unstable in the presence of alkali. NaOH is a strong alkali and quickly sees off the colour of iron blue in a silver print.
    Similarly, Selenium is not likely to be involved in this IMO, for the good reasons you have mentioned and I think both of these are 'red herrings'.
    From what you said in your 1st post you are not sure of the ingredients of this toner. From your description, it seems likely that it is a thiourea toner, but I have used thiourea toners regularly and frequently for many years and don't recall getting blue metallic shadows in any of them - unless combined with another agent such as a metal ferrocyanide, so it would definitely be worth contacting the manufacturers, explaining your problem and asking if they can help with an explanation, or at least provide you with an ingredient list or MSDS data sheet. This just might shed some light on your problem.
    this may possibly not be what you want to hear, I know, but it's usually best to start with first principles and basic data ;-)
    kind regards
    Tim
     
  10. Marco B

    Marco B Member

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    Yes, I think I will need to do that, and contact the manufacturer.

    One thing intrigues me though. You disqualify of the possibility of Prussian blue being formed, yet you do point to the possibility of a metal ferrocyanide (which Prussian blue is also). However, according to this excellent article by Wilco Oelen:

    http://www.woelen.nl/photo/toner.pdf

    *all* metal ferrocyanide compounds are supposed to be instable in alkaline environments. The article is about a vanadium toner, but explains some of the metal ferrocyanide toning chemistry as well. For the alkali susceptibility, see the section "Chemistry of extensions of the toner".

    So in what direction are you possibly thinking :confused:

    Thanks for your response by the way...
     
  11. Bob F.

    Bob F. Member

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    Just to confuse things further: the stains I had were only silvery rather than having any blue sheen and, if not too extensive, could sometimes be "rubbed out" with a gloved finger in the toner. It only happened a few times so I never really tried to investigate.

    I suspect we had different events (though they might be chemically related) - unfortunately I lack the chemistry to be of any use in considering possible causes...

    Cheers, Bob.
     
  12. Marco B

    Marco B Member

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    Bob: I agree with you that the stains are far more silvery than "bleu-ish", so I do think we witnessed the same effect. And I also confirmed your "rubbing out" effect (in my case by agitating the tray a little bit more). The stains are however, only removable, when still in aqueous environment of the initial toning...

    My chemistry is from my high school days and a university biology study. Gets me there in understanding the basics, but I'm not an expert either...:sad:

    Tim: I have requested the data sheet from the manufacturer, as you suggested. Let's see what they come up with... If there is any useful information about the chemical composition, I'll post it here.
     
  13. Marco B

    Marco B Member

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    Hi Tim (and Bob and others),

    Sorry for the delay in responding. Hope you still have this thread in your "watch" list.

    I have now received the datasheet from the manufacturer. Not much surprises though, it's indeed a thiourea based toner, with the following composition:

    Bleach bath:
    - Potassiumbromide 5-20%
    - Potassiumferricyanide 5-20%

    Toning bath:
    - Thiourea <1%
    - Sodiumhydroxide 2-5%
    - Potassiumcarbonate 5-20%
    - Potassiumbromide 1-5%

    According to the manufacturers instruction manual for the toner, this stock solution (the toner comes as a liquid!) needs to be diluted 1:9 to get at the working solution strength.

    The only things that slightly puzzle me are the very low thiourea contents, and potassiumbromide in the toning bath. Thiourea being the active compound for donating the sulphide anions, I would have expected some higher content. But maybe my feeling as to the contents of silver in a print is simply completely wrong, and only little thiourea is needed to convert that silver... Well, the toning bath works well anyway when not exhausted :tongue:

    I wonder what the function of the potassiumbromide in the toning bath is. I have seen some recipes for thiorurea baths once on a webpage, and none had potassiumbromide in the toning bath...?

    Lastly, I recently visited a museum exposition that included some beginning of the 20th century pictures (1900-1920). Some of them showed a similar "metallic" sheen in the darkest parts of the images (which I presume were also sepia toned judging the color). The stains really looked VERY MUCH like my stains on my dried prints...

    I now begin to wonder, having read the book by William E. Leyshon that I recently posted about on this thread:

    http://www.apug.org/forums/forum42/42869-nice-book-about-alternative-19th-century-processes.html

    if the metallic sheen on my prints is actually simply a "tarnishing" layer??:confused: Maybe that the exhausted toning bath, that maybe includes harmful reaction products as well, can cause a rapidly accelerated "tarnishing" process on prints :confused:

    Well, it's another wild theory, hope you can shed some light on this... I also intend to do some more research / reading on tarnishing anyway, since I'm interested in the details behind toning and archivability of photos.

    Marco
     
  14. KWhitmore

    KWhitmore Member

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    I've also experience a similar shiny metallic-like deposit from a homemade ferri/bromide and thiocarbamide/sodium hydroxide bleach and toner combo. The only pic out of the whole batch of toned prints that displayed the shiny bits was the Kentmere Fineprint VC fiber. Trouble is, I can't tell you whether it was one of the first bunch or the last that went into the toner in order to rule out toner exhaustion.
    Someone (Dave maybe?) mentioned fixing after this sort of toning...what were the results? Did fixing remove the metallic sheen? My notes say only to wash and re-fix if the full density of the print doesn't return after toning. I'm going to try and post my example.

    Kathy
     
  15. Sparky

    Sparky Member

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    I've actually had that result on 'normal' prints a few times - though it was VERY long ago and I hadn't had it since. I imagined to myself it was due to hard local water... but I'm not so sure about that at the moment now. Indeed it resembles what is called 'silvering' on vintage silver gelatin prints - I could easily imagine it is the very same process which has been elicited chemically by some impurity, mishandling or other... perhaps something in the air...?
     
  16. KWhitmore

    KWhitmore Member

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    Here's my shiny example....
    [​IMG]
     
  17. Dwane

    Dwane Member

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    Marco - Are you applying the liquid emulsion onto paper? It might be possible that you are not washing the fixer completely out of the paper, allowing the fixer to interact with the toner, causing the staining you're seeing. The hypo might be more difficult to wash out of the paper your using compared to regular fiber based photographic paper, and require longer washing times. And there might also be some chemicals in the paper itself that are interacting with the liquid emulsion and toner. Just a thought.
     
  18. Philippe-Georges

    Philippe-Georges Member

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    At the time, when AGFA still existed, I had the same problem on MCC111FB.
    Thus I asked AGFA for advice, and they told me to soak the print in a fresh 1 % glacial acid bath for about 1 min. and wash the print afterwards as usual for FB paper, the stains were gone!
    They never told me what caused it, so, when ever I have a problem after toning, the 1 % glacial-acid is near.
    The same for the problem of that chalky feeling FB paper sometimes can have after multiple (split) toning.

    I do not know if this will work for you, but it would not harm to give it a try, I hope so.

    Good luck,

    Philippe
     
  19. Marco B

    Marco B Member

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    Hi Kathy and others,

    Thanks for posting your example of the metallic sheen. Yes, it does very much look like my stains. Also clearly noticeable is the preference for the dark parts of the image. This example also very much resembles what I saw on these beginning of the 20th century pictures.

    Phillipe: are you sure your stains were clearly "metallic"?? As Tim wrote:

    "Thiourea sepia often leaves a white deposit which dissolved in 3% acetic acid or simply some dilute stop bath, but it doesn't look metallic (to my eye)."

    I've had these "white deposit" stains sometime as well, it's most likely simple calciumcarbonate / calcareous deposit caused by non-demineralized water, as indeed they are removable with acetic or glacial acid, as I could confirm Tim's recommendation. However, these stains, although they somewhat look like the "metallic" stains, are not as metallic, nor are they exclusively limited to the darker parts of the image. So I think this is another issue...

    I intend to get the book "Care and identification of 19th century photographic prints" by James M. Reilly. According to Leyshon, there should be a chapter describing the processes underlying "tarnishing" in that book.

    I already know I can get it in the Amsterdam library, but it needs to be specially ordered, as it is in the storehouse of the library... may take some time.

    Marco