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  1. #11
    colrehogan's Avatar
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    It's not so much the contribution of the Pt metal to the formula, but a matter of the Pt metal changing oxidation states in an oxidation/reduction reaction. The difference is the oxidation state of the Pt metal in each solution. In Na2PtCl6 (sodium chloroplatinate) the platinum has a 4+ oxidation state. vs. the K2PtCl4 (potassium chloroplatinite) in which the platinum has a 2+ oxidation state.
    Diane

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  2. #12
    Joe Lipka's Avatar
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    Can you translate that into English?
    Two New Projects! Light on China - 07/13/2014

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  3. #13

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    Joe, the way I think of it is: NA2 tans darker values faster with a bit more contrast. Kind of like printing multiple contrast does in silver. At the exposure level rather than in the devloper. doing it at the developer level seems to push existing imformation within the emulsion further which seems to effect the grain. Kind of like push processing.
    I don't know all the teck talk stuff so this is an observation only.
    Stop trying to get into my mind, There is nothing there!

  4. #14
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    In simple terms, the Na2 consumes twice as much ferrous oxalate (ferric oxalate is converted to ferrous by UV light) than the palladium salt during the final reaction where ferrous converts back to ferric and causes the metals in the paper to reduce to the tiny particles that end up embedded in the fibers of the paper to form the image. Because it consumes the sensitizer at twice the 'normal' rate, it has a preferential effect in restraining the development of highlights, which have very little 'activated' sensitizer anyway. This causes the increase in contrast in the final image.

    By way of a simple example, say a highlight area has 4 molecules of 'activated' ferrous and a shadow has 128 molecules of the same. Two extra molecules of Na2 in each print area would totally consume the 4 molecules of ferrous in the highlights, leaving none to convert the remaining palladium. The same thing happens in the shadows, but the reduction is only taking 4 out of 128 molecules of ferrous out of commission, leaving the rest (128-4=124) to reduce the palladium to image forming particles. The net result is hardly any effect on the resulting print density in the shadow areas on a percentage basis, but a profound effect in the resultant print density of the highlight areas.

    This is vastly simplified, but that is basically how the contrast agents all work. The differences between the contrast agents come about in the side effects they create. The chlorates tend to cause the image-making particles to clump together and cause graining, while Na2 does not have this annoying tendency.

    That is probably way more than anyone cares to know about this stuff. The simple fact is that the Na2 is just a good contrast increasing agent without the bad side effects that come with using chlorate in the sensitizer.


    Quote Originally Posted by colrehogan
    It's not so much the contribution of the Pt metal to the formula, but a matter of the Pt metal changing oxidation states in an oxidation/reduction reaction. The difference is the oxidation state of the Pt metal in each solution. In Na2PtCl6 (sodium chloroplatinate) the platinum has a 4+ oxidation state. vs. the K2PtCl4 (potassium chloroplatinite) in which the platinum has a 2+ oxidation state.

  5. #15
    Kerik's Avatar
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    Awesome! That's the best explanation I've read on how Na2 works. (Below is an artist's rendition of Clay explaining this phenomenon.)
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  6. #16
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    You should see my new Christmas beanie. It plays Jingle Bells when the propeller turns.

    Quote Originally Posted by Kerik
    Awesome! That's the best explanation I've read on how Na2 works. (Below is an artist's rendition of Clay explaining this phenomenon.)

  7. #17

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    Kerik,

    I know a person who wears double-breasted shirts with TWO pocket protectors. He calls it 'full frontal nerdity'.

    ---Michael
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    B&W photography in Silver, Palladium, and gum bichromate.

  8. #18
    colrehogan's Avatar
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    I guess Clay and I don't speak English, we speak chemistry.
    Diane

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  9. #19
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    so Ive edited this thread title so its more fitting to the topic. Hopefully thatlly make it searchable. good explanation clay.

  10. #20

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    It still needs a bit of dumbing down. Is It light reactive or chemical reactive? I only have one pocket and no protecters.
    Stop trying to get into my mind, There is nothing there!

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