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  1. #11

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    Perhaps the mere presence of a developing agent does not make a paper "developer" incorporated;
    Developing agents are not rare, and if those present can't actually be used for processing, then they are not there to function as "developers" and there is thus no ID.

    Logically illogical?

  2. #12
    Ian Grant's Avatar
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    If a developing agent is in an emulsion then it just need the other ingredients of a developer to function, and NaOH is sufficient.

    Sodium Sulphite is a very weak developing agent so where do we draw a line, an adjunct to aid faster processing may show a weak developing effect but not be considered a developer in normal circumstances

    Ian

  3. #13
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    A developing agent is a discriminating reducing agent. Thus HQ and Metol are developing agents and reducing agents. Stannous Chloride is a reducing agent but is non-discriminating and thus is a fogging agent but not a developing agent. Sodium Sulfide is a strong reducing agent and non-discriminating. It can act as a non-discriminating developer, a fogging agent or a reducing agent.

    The Ilford paper contains an agent which will develop the Silver Halide when presented with an activator solution. Now, make of that what you wish, a reducing agent is present which will develop a brownish black image in alkali in the samples I tested. If it caused fog, then under normal conditions, the paper would fog.

    It may be there as a preservative for all I know, but it meets my criteria. That is all I can say. I would not suggest using it in an activator due to the poor image quality. So, whatever it is, it is rather weak.

    PE
    Last edited by Photo Engineer; 01-25-2010 at 04:21 PM. Click to view previous post history. Reason: Changing Silver Sulfide to the correct Sodium Sulfide - thanks Ray for catching this.

  4. #14

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    Yes, I agree.

  5. #15
    Ian Grant's Avatar
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    Yes

  6. #16

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    Quote Originally Posted by Photo Engineer View Post
    A developing agent is a discriminating reducing agent.
    Silver Sulfide is... non-discriminating. It can act as a non-discriminating developer....
    PE
    Uht-Oh... I'm confused! :o
    Was this a typo?

    Stannous Chloride is
    a non-discriminating reducing agent
    and thus not a developing agent.

    Silver Sulfide is
    a non-discriminating reducing agent
    and [thus a] non-discriminating developer.


    A non-discriminating developer = not being a developer, as does all non reducers, correct?

  7. #17
    Rlibersky's Avatar
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    Thanks for the information.

  8. #18
    Photo Engineer's Avatar
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    Quote Originally Posted by Ray Rogers View Post
    Uht-Oh... I'm confused! :o
    Was this a typo?

    Stannous Chloride is
    a non-discriminating reducing agent
    and thus not a developing agent.

    Silver Sulfide is
    a non-discriminating reducing agent
    and [thus a] non-discriminating developer.


    A non-discriminating developer = not being a developer, as does all non reducers, correct?
    Ray;

    That should read Sodium Sulfide.

    Sorry. It is used in reversal B&W processes to act as the second developing step after the bleach.

    PE

  9. #19
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    Quote Originally Posted by Photo Engineer View Post
    In spite of their words to the contrary, Ilford MGIV paper tests medium positive for incorporated developing agent(s). It is not useful to wash a developing agent out as other useful chemistry might go as well.
    PE
    I agree with this. There are a lot of threads on APUG insisting that MGIV does not have incorporated developer and that might be true but there are acceleration agents or something. Last night I played for quite a while with some cut up pieces of lumen prints on MGIV and they develop a dark grey very quicky when dipped in 2oz water + 1/2 tsp sodium carbonate. I can't get to full black and the development appears to exhaust fairly quickly: after the initial 15 seconds or so, no further development happens in "washing soda water".

    This makes me wonder how much of the paper development with caffenol I've read about is just from alkaline solution and how much is from the homemade developer or coffee part.

    I was trying to produce an extremely slow working developer for paper, and thought an old unwanted lumen print would make a good test subject. Pretty soon I was just playing with room light exposed paper strips, at my desk in room light.

    I managed to produce one very interesting effect. I took a little snippet of a lumen print with whitish plant stems on it, surrounded by pinkish purple. This I dipped in the "soda water" and then quickly into a cup of coffee ( would be slightly acidic, I think) . I managed to stop the development at a lower point. Then I blasted the snippet under my desk lamp for about 15 or 20 seconds and started dipping it back and forth between the coffee and the soda.... the background only darkened a little more, but the original light colored stem turned a dark purple color. I think I might have produced something similar to the so-called Sabattier effect.. or maybe just some kind of self-masking & developer exhaustion combination. Whatever it was, I did get a reversal, even though the final result was lower contrast. I'm intrigued and will probably play around with this some more.

    Do you think it might be possible for me to reduce the ph enough not to activate the developing agents/accelerants in the emulsion, or at least slow them down enough to get the process more under control? I'm interested in setting up a "snatch point" rather than developing to completion.

    I guess I'll find out for myself... I'll try a lower concentration and maybe some sodium bicarbonate to restrain the ph.

    Anyway, I stumbled across this thread and it is very true that modern recently made MGIV will "develop" just in water +sodium carbonate, to a dark grey but not black.

  10. #20
    Photo Engineer's Avatar
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    It is impossible to predict. Ilford insists that there are no developing agents present, but MGIV tests mildly positive.

    PE

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