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  1. #21
    Marco B's Avatar
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    Quote Originally Posted by sanking View Post
    Marco,

    Would you direct me to a source in the literature that discusses conversion of the non-gold replaced silver to silversulfide with gold thiorea toners? I am very interested in reading more.

    Sandy
    Sandy, I don't have such literature, but thiourea is also (at least weakly), a direct toner, as I know of my own experience. Normally, it is used as an indirect two bath bleach / redevelop sepia toner with ferrocyanide as the bleaching step.

    Now I am not a chemist, and know little about gold toning, but if it weren't for the toning effect, why would thiourea be added to a gold/thiourea toner at all??? What other function would it have?

    It just seems logical that it is added for its toning effect. But I might be missing some other chemical function of it in gold toner...
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  2. #22

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    I'm not a chemist and/or know the chemistry behind, BUT, I presume gold chloride + thiourea is forming a relatively stable gold thiocarbamide complex. ??? Mind gold thiocyanate toner; the working solution is not very stable and has to be mixed right before using whereas gold thiourea toner working/stock solution is very stable (relatively!), it has a very good shelf life... It's very practical compared to gold thiocyanate. Maybe that's the reason of using thiourea with gold chloride. ???

    As for toning effect of thiourea (if free thiourea exist in the compounded toner, that is), I think that's highly pH dependent; remember that you have to add alkali activator to the toner stock solution. What's the pH of the gold-thiourea toner?

    Anyway, this is pure speculation; just some food for thought... The only thing I know is that gold-thiourea toner is great and it was my only choice for iron-silver prints.

    Regards,
    Loris.

  3. #23
    Marco B's Avatar
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    My suggestion was also pure speculation... unless someone turns up a document showing the chemical processes going on in gold/thiourea toning, I don't know for sure.

    Nice document by the way I just hit upon on an UNESCO website:

    The Preservation and restoration of photographic materials - PDF document

    And a bizar method for the ultimate negative intensification if you screwed up and severly underdeveloped your negative (Warning, radioactivity here!!!)

    http://www.freepatentsonline.com/4323641.html

    Marco
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    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  4. #24
    Marco B's Avatar
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    And of course there is Mike Ware. He developed the Chrysotype alternative process utilizing gold, if anyone could answer these questions it is him...

    http://www.goldbulletin.org/assets/f.../ware_3_39.pdf

    Loris, you might consider contacting Mike. Looking at some of the chemistry in this document by the way, your remark about the stabilizing effect of the thiourea might be right, but I am not sure. Mike mentions some other chemicals (ligands) to stabilize a gold solution.
    Last edited by Marco B; 05-31-2010 at 12:46 PM. Click to view previous post history.
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  5. #25

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    I didn't expect the post to generate such an interesting debate, thanks all it is great stuff. I just wish I had paid attention in my chemistry classes instead of daydreaming about being in the Clash. I may get in touch with Mike Ware to see where one can get gold chloride in the UK. Mind you reading his article it would make me sound a complete philistine if that was all I asked him so maybe I better not!

  6. #26
    Marco B's Avatar
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    Quote Originally Posted by Mac064 View Post
    I may get in touch with Mike Ware to see where one can get gold chloride in the UK. Mind you reading his article it would make me sound a complete philistine if that was all I asked him so maybe I better not!
    Mike seems to be quite an accessible and amiable chap... Loris knows all about it...
    My website

    "The nineteenth century began by believing that what was reasonable was true, and it wound up by believing that what it saw a photograph of, was true." - William M. Ivins Jr.

    "I don't know, maybe we should disinvent color, and we could just shoot Black & White." - David Burnett in 1978

    "Analog is chemistry + physics, digital is physics + math, which ones did you like most?"

  7. #27
    nze
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    I don't if this double toning will work. I just make some test with toned argyrotype print that then put in a solution of nitric acid to convert silver in silver nitrate.

    With single toned print There is no loss in the highlith but a little loss in the lowlight ( about 10% reading of the grayscale)
    With double toning the loss is so insignifiant that it is not visible.
    Chris Nze
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  8. #28

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    Christian, what is your double toning procedure? One toner is gold-thiourea (if I'm getting it right), what's the other and in which order do you tone? (My wild ass guess would be partial pt or pd toning then gold... ???)

    TIA,
    Loris.

  9. #29
    nze
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    that's just starting with a noble salt toner, wash and then put in another salt toner. The toner can be use in the following order Gold, platinum palladium. I use the folrmula given by Sandy king in his article on unblinkingeye, but dilute them twice to slow down the toning.
    Chris Nze
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  10. #30

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    Quote Originally Posted by nze View Post
    that's just starting with a noble salt toner, wash and then put in another salt toner. The toner can be use in the following order Gold, platinum palladium. I use the folrmula given by Sandy king in his article on unblinkingeye, but dilute them twice to slow down the toning.
    Do you just add the second toner to the tray with the first, or rinse the print and then add the second toner?

    Sandy

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