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  1. #51

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    NER - did you know that XTOL generates a stain? It does, bleach some XTOL processed film and you will see a very faint magenta stain. It's not enough to have a significant effect, but it is visible.

  2. #52

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    Kirk, he's going to ask you where you read that, so hit the books!

  3. #53
    NER
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    Quote Originally Posted by Helen B
    Norman wrote:
    "...I defer to Mees, Tull, Neblette, Hauff, Bogisch, Lumiere, Andresen, Haist and researchers of similar reputation whose reports were both authoritative and accurate, and did not - to the best of my current knowledge - mention anything about hydroquinone image stain. ..." My emphasis.

    Before I quote something else, I'd just like to say two things:

    -I'd trust the guys here who say that hydroquinone forms a stain image even if I didn't already know it, and

    -few of the standard texts (or at least those I have) go into much detail on stain images, if they mention it at all, but they do cover tanning. Tanning and staining may not be the same, but they are similar, and if the developer oxidation product is coloured then there is likely to be a link between tanning and the formation of a stain image.

    OK, so on to L P Clerc's Photography Theory and Practice, 1971 edition revised by R. E. Jacobson, Vol 4, Monochrome Processing:

    "573. Oxidation Products of Developers; Tanning; Secondary Images.
    The quinonoid oxidation products of developers that are formed in the absence of sulphite, or in the presence of very low concentration of sulphite, are deposited in the gelatine at the site of development, and in a quantity proportional to the amount of silver halide reduced. Usually they polymerize, giving rise to coloured, tanning substances of the nature of humic acids, whose exact constitution is unknown.

    After removing the silver image ... a yellow or brown secondary image remains, which, though it may not appear very intense to the eye, can give acceptable prints on high contrast paper because of its absorbtion of actinic light. The following table (Lumière and Seyewetz, 1928) shows the colour of the secondary image obtained in various developers, its relative intensity and the concentration of sulphite necessary to prevent its formation.

    Developer -- colour -- relative intensity -- sulphite g/litre

    Pyro -- yellow-orange -- 10 -- 11
    Catechol -- black -- 10 -- 6
    Hydroquinone -- yellow-brown -- 10 -- 2
    Chlorhydroquinone -- yellow-brown -- 10 -- 2
    Amidol -- reddish-brown -- 8 -- 2
    p-Aminophenol -- brownish-black -- 3 -- 2
    Metol -- brownish-black -- 2 -- 1
    PPD -- Grey -- 1 -- 0
    Glycin -- None."


    Best,
    Helen
    Thank you very much for the citation and quote.

  4. #54
    NER
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    Quote Originally Posted by psvensson
    Kirk, he's going to ask you where you read that, so hit the books!
    Why is asking for verification of a statement so unusual and a cause for ridicule?

  5. #55

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    Quote Originally Posted by NER
    Why is asking for verification of a statement so unusual and a cause for ridicule?
    He just told you what he has observed. To ask him to "verify" the evidence of his senses by citing a peer-reviewed work seems more than a little superfluous.

  6. #56
    NER
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    As you can see, I did not respond to the point about XTOL. I thought you were referring in a more general way to the preceding discussion.

  7. #57

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    NER - I think he was referring to the general tone of the preceding discussion. Don't worry about it.

  8. #58
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    I find this argumentation quite amusing. In my years of experience as a research engineer, I have seen several instances where theory was cited as a reason for some experiment not working, whereas in fact it did work.

    One thing you must remember. In years gone past, the image stain left by development was a nuisance to be avoided. You could get that impression from the works of Hurter and Driffield. It happens that the stain left by hydroquinone is mostly avoided by having anything like the usual amount of sulfite in a working solution. Furthermore, in order to get the optimum superadditivity between hydroquinone and either metol or phenidone, a certain amount of suldite is required. That is almost as much as it takes to prevent staining. The ordinary experimenter would not see any staining by hydroquinone, because who compounds an MQ or PQ developer without at least 10 grams of sodium sulfite per liter? I found it for myself because I was interested in sulfite-free developers. Not for environmental reasons, but because sulfite free developers tend to be surface developers that are not hindered as much by the surface charge barrier (I hope I got it right, but really don't care.) You can find such statements in "The Theory of The Photographic Process".

    So, I thought I found that hydroquinone in alkaline solution does make a staining developer. Then I found by reading a book that I was right, by gum! I'm glad I found that book. Otherwise I might be hiding in a corner in denial somewhere, fearing I had seen an imaginary ghost image.
    Gadget Gainer

  9. #59

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    Quote Originally Posted by psvensson
    Quote Originally Posted by srs5694
    Perhaps there's something more explicit in the body text somewhere, or in another issue.
    Yes, there is. I don't have the issue in front of me, but he does say something like "Bet you didn't know hydroquinone can be a staining developer." He was right about that!
    I thought I remembered such a comment, too, so I went and skimmed the rest of the article, and it's on p. 25: almost exactly the phrase you use, in parentheses, followed by "Hydroquinone is 1,4-dihydroxybenzene. Pyrocatechol is 1,2-dihydroxybenzene. According to theory(1), any developer with two or more active hydroxyl groups will be an active tanning and staining developer." The footnote ("(1)" above) then offers chapter 13 of W. H. Lee's _The Theory of the Photographic Process_ as a citation. I don't happen to have that book to cite it directly, though.

  10. #60

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    Quote Originally Posted by Helen B
    " ... Tanning and staining may not be the same, ... "

    One and the same I'd say.

    " .... if the developer oxidation product is coloured then there is
    likely a link between tanning and the formation of a stain image."

    The PRODUCT of the reaction TWIXT the oxidation product and
    gelatin is a colored, tanned, gelatin.

    "L P Clerc's ... and in a quantity proportional to the amount of
    silver halide reduced. ... they polymerize, giving rise to coloured,
    tanning substances of the nature of humic acids, ... "

    So, there it is from L P Clerc; tanned gelatins of various
    colors are the result of a reaction twixt the developer oxidation
    products and the gelatin. And below some more from Mr. Clerc.

    "Developer - colour - relative intensity - sulphite g/litre

    Pyro -- yellow-orange -- 10 -- 11
    Catechol -- black -- 10 -- 6
    Hydroquinone -- yellow-brown -- 10 -- 2
    Chlorhydroquinone -- yellow-brown -- 10 -- 2
    Amidol -- reddish-brown -- 8 -- 2
    p-Aminophenol -- brownish-black -- 3 -- 2
    Metol -- brownish-black -- 2 -- 1
    PPD -- Grey -- 1 -- 0
    Glycin -- None."

    Best, Helen
    I can only wonder what is going on with that hydroquinone.
    That 2 grams/liter is also a Lith developer sulfite maximum.
    Reconcile, if you will, HQ's oxidation products giving lith
    development and at the same time those oxidation
    products being involved in tanning gelatin. Dan



 

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