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Thread: Coating Wicking

  1. #1

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    I have found a wonderful paper that I wish to use for Pt/Pd printing. This stuff is smooooth and can take an extended soak time (hours) with no dog ears or separation of surface fibres. However, it is a thirsty paper and the coating travels the surface like a nomadic tribe.... So for now I shall fondly refer to it as Sahara Satin.

    The problem I am experiencing with this paper is as follows...

    The paper drinks the first coat deeply but evenly, a print from this is beautifully smooth in tone but slightly anaemic. When two coats are applied to the paper the mysterious migration begins. It proceeds from the centre to the edge of the previous coat then when it encounters the coating edge it begins to return toward the centre. This results in a print with a rich black velvet border but the continuity of tone diminishes toward the centre of the image. With a third coating there is minimal migration however the entire image has a distinct veiling that is most apparent in the blacks.

    Now I believe that various research has demonstrated platinum chemistry is inhibited by gelatine, so this is probably not a solution to my problem. I would appreciate any ideas or methods that I could try to get this paper to work for me... overcoats, undercoats, sweater vests... Anything.

    And.... Yes of course if I can find a method to make this beautiful paper work I will certainly post all the details here.

    Thanks!!

  2. #2
    clay's Avatar
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    The only thing I can suggest that might be worth trying is to add a few drops of polyvinyl alcohol to about 125-150% of your normal sensitizer volume before coating. It is a sizing agent, and will keep the stuff on the surface of the paper longer, while the increased volume may help the print anemia. I would let it dry to a matte finish (about 2 minutes) and then finish drying with a hair dryer.

    Try that and see if it helps at all. This is just a guess. B&S has polyvinyl alcohol in case you don't have any on hand. BTW, does your print float or sink in the washing tray? My rule of thumb is that PVA and forced air drying is needed on paper that sinks. Not always the case, but a good hint anyway.

  3. #3

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    In addition to Clay's suggestion, why dont you try a pre bath with oxalic acid. What you are describing is called capillary action and it due to differences in humidity within the paper.

    So you can approach this problem in two ways, either humidify the paper completely, or "wet" the paper entirely to insure you have uniform humidity once it dries.

    My initial choice would be to give it an oxalic acid pre bath, if you do not want to do this, then open the hot water faucet and let the steam humidify your paper, this might help.

    Good luck.

  4. #4
    Kerik's Avatar
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    Now I believe that various research has demonstrated platinum chemistry is inhibited by gelatine,

    What makes you believe this? Many papers we use are gelatin sized at the factory and I know several printers who routinely gelatin size certain papers prior to applying the pt/pd sensitizer.

    Kerik

    ps Are you going to tell us the name of the paper you're using?

  5. #5

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    Kerik, I found several references about gelatin inhibiting Pt right now I can only find this historical one....

    "We find evidence from an early stage (1880) of Willis's awareness that platinotype chemistry is inhibited by gelatin. He therefore avoided it as a sizing agent for his papers..."

    There was also a more recent reference that actually explained what was happening in terms of the chemical process and as I recall the Pt was more inhibited than the Pd..... I will try to find that link tonight.

    I do not know the name of the paper..... I found a simple way to strip the emulsion from PX 3001 (yes I can hear you all groaning in disgust... but the paper surface is gorgeous and the paper is strong).... I think that if I can find the right resizing agent it will be a viable paper for me... sorry to disappoint.

  6. #6

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    I just received a nasty slam off forum about the nature of my postings here ....... I'm GONE...... !!!

  7. #7
    clay's Avatar
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    Annie and Kerik:

    I'll bet the reference about gelatin came from here:http://www.mikeware.demon.co.uk/prep.html. Look at the paper paragraph where he talks about gelatin being inimical to pure platinum prints, but okay with palladium. That is one of the reasons he says that Buxton can still be used to make truly 100% platinum prints, since it is sized with alki-something dimer-something.

  8. #8
    Ed Sukach's Avatar
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    Quote Originally Posted by Annie
    I just received a nasty slam off forum about the nature of my postings here ....... I'm GONE...... !!!
    Set up aother vote here ... I propose that whoever caused this to happen be KICKED OFF without ceremony. Let us all know who and that it happened!!
    Carpe erratum!!

    Ed Sukach, FFP.

  9. #9
    Ole
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    I second that motion.
    -- Ole Tjugen, Luddite Elitist
    Norway

  10. #10

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    Just wanted to clarify one thing, my 'fan mail' did not come through a PM here on APUG but to my e-mail at Yahoo which has been available on several photo forums on which I use the same name as here. The header for the message indicated that it had to do with my posting on APUG. However when a message begins with You Stupid B---h one assumes it is not good news and I immediately deleted the message emptied the trash and checked my computer for viruses.

    The postings on the forum are available to all and this person may have passed through at any time and the fact that I received this message while this thread is active may be coincidental.

    However, I will not leave one moment of my life open to this kind of verbal assault and will no longer be posting here or the other forums and have left my Yahoo e-mail address to oblivion.

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