The placement of Iodide in emulsions

Discussion in 'Silver Gelatin Based Emulsion Making & Coating' started by Photo Engineer, May 25, 2017.

  1. OP
    OP
    Photo Engineer

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    Fuji did some work on this IIRC but it really was only useful in the slower ranges AFAIK.

    PE
     
  2. kb3lms

    kb3lms Subscriber

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    Many of the formulas we see start off with Iodide in the kettle. Since this traps the iodide at the core (because it precipitates first), why is this done? It seems to me that the effects of iodide would be more pronounced in that it would produce more dislocations if it were added throughout precipitation. Or, add iodide near the end of precipitation, thereby making a shell of AgBrI over an AgBr core. Is this something that is done in modern emulsions?
     
  3. OP
    OP
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    Well, if you run Iodide, Bromide and Silver, you get a gradual progression to AgBr and thus make a core shell which you can treat as you wish. Or, you can make high Iodide emulsions by just running Silver into this mixture with the right halide.

    PE
     
  4. thio

    thio Member

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    afaik the modern tabular grain emulsions consists of core-shell microcrystals.
     
  5. guangong

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    PE, could you relate your comments on iodine to Bergger panchro 400 film?