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  1. #1
    martellsv's Avatar
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    Chemical catalyst

    If one developing agent work slowly, could i use a catalist to improve the speed, reducing the induction period?
    considering the propierties of the catalist.... over the silver halide...
    Thanks Alejandro Spain

  2. #2

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    Not sure exactly what you're asking, but the activity of typical developing agents increases as pH increases. Developers contain an alkali "accelerator" for this purpose. Is this what you're referring to, or are you referring to an actual catalyst?

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    I have the same problem as Michael has. What is the purpose of your question? Is it merely curiousity or is there a practical reason for your question. Without more information it is hard to give an answer.

    To add to what Michael said, the activity of a developing agent increases with temperature. In certain cases there are chemicals that can be added to a developer to increase its activity. These chemicals reduce the charge barrier effect. For example certain quartenary salts can reduce the induction period. Mason in his book Photographic Processing Chemistry Chapter IV discusses the mechanism of development in detail.
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  4. #4
    martellsv's Avatar
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    For example certain quartenary salts can reduce the induction period.

    Quote Originally Posted by Gerald C Koch View Post
    I have the same problem as Michael has. What is the purpose of your question? Is it merely curiousity or is there a practical reason for your question. Without more information it is hard to give an answer.

    To add to what Michael said, the activity of a developing agent increases with temperature. In certain cases there are chemicals that can be added to a developer to increase its activity. These chemicals reduce the charge barrier effect. For example certain quartenary salts can reduce the induction period. Mason in his book Photographic Processing Chemistry Chapter IV discusses the mechanism of development in detail.
    I tried to use one ammonium quaternary salt, but i understood some work better than other salts that i haven't got.... perharps imidazoles? Moersch use it with only Hydroquinon developers you can find the MSDS easily. That book is hard to find in Spain, and in the www.
    IMHO, (using a metal calalist) change the shape / structure of halide crystal to offer no resistance to the penetration of developing agent (only Hydroquinone) perhaps metal (copper or manganese Mno2 perhaps). no, I'm not chemical is an idea ... stoichiometrically no change ... Perhaps This will change the ionic status negativ-negativ (repulsion) to neutral-negativ Thanksssss

  5. #5
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    Be aware that MSDS only list toxic components and only those which are contained in sufficient amount and then only those which are not proprietary. If MSDS would tell you the whole story, Fuji would fix with sodium metabisulfite only ...

    A number of development accelerators have been described in patent literature. I don't think you want to change the shape/structure of the halide crystal, since these are carefully designed to have exactly the properties they have for optimum results.

    Some have already mentioned alkali, which increases developer activity of most common developers. You brought up tertiary ammonium salts, note that tetramethyl ammonium salts are extremely toxic even with skin contact, so you might stick with tetrabutyl ammonium salts, which are affordable and obtainable. US patent 5962202 describes a developer with tertiary ammonium salts and ascorbic acid. While Phenidone and Metol are not catalysts (as I have been told), they do reduce the induction period for Hydroquinone, Catechol, Ascorbic Acid and others.
    Trying to be the best of whatever I am, even if what I am is no good.

  6. #6
    martellsv's Avatar
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    Neutralize

    tetrabutyl ammonium salts, ok Thanks,

    I wonder if putting a metal deposit I can try to neutralize the barrier, not change the halide with a catalist, I donīt Know thanks... I think this function canīt be supplied exactly with alkalies... for several reasons, prehaps the most important is if you want to take an elevator to the sixth floor down not settle for the third, and if you can do it in 6 minutes better than in twelve, thanks
    I am convinced of the qualities of hydroquinone beyond of Metol and PD, in some cases

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    Doubling the concentration of your developer will decrease time, if that's what you're really after. Look at the development times for HC-110 A versus HC-110 B, or Rodinal 1:25 vs. 1:50 or 1:100.

    Peter Gomena

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    Rudeofus's Avatar
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    Quote Originally Posted by martellsv View Post
    I wonder if putting a metal deposit I can try to neutralize the barrier, not change the halide with a catalist, I donīt Know thanks...
    Do not put any metal near the grains, or no developer will ever be able to distinguish between exposed and unexposed grains! An exposed grain has maybe only a few silver atoms, you better don't mess with these and you sure don't want to put metal atoms on unexposed grains, or you might as well substitute your dev with black spray paint.

    Quote Originally Posted by martellsv View Post
    I think this function canīt be supplied exactly with alkalies...
    You are correct. Alkalis increase the reduction potential of common dev agents, but don't make the HQ/AA stick to silver any better. A nice example for this is HQ which reduces silver halide in caustic environment, whereas Quinone is a good (albeit smelly) bleaching agent in acidic environment, i.e. you can even reverse the direction of the reaction with pH.

    Quote Originally Posted by martellsv View Post
    I am convinced of the qualities of hydroquinone beyond of Metol and PD, in some cases
    Can you give us any indication why you are so convinced of this? Is it just gut feeling or do you have some experimental data to support your stance?
    Trying to be the best of whatever I am, even if what I am is no good.

  9. #9
    martellsv's Avatar
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    Emulsion

    I think is possible put traces of Gold, in the emulsion to sensitize it e.g, i have experimented with iron compounds (other reasons and sorry i havenīt seen the effect you have described)....
    I think it could be chemicali possible to fatten the silver... with metal incorporating it into the filaments of silver with very few traces (but this is not the reason)...
    A catalist is possible with very few quantities to neutralize the barrier ?????

    Probably you have the reason... i only try to undertand more...thanks
    I think like explain the hydroquinone cuestion...thanks

  10. #10
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    Gold added at the rate of about 1 part to 3 parts of Sulfur are used in making the emulsion, but during processing Gold has little (if any) effect. Cobalt Hexammine and Hydrogen Peroxide are known to be heterogeneous catalysts in color development, but this is not what you are looking for.

    PE

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