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  1. #11
    ben-s's Avatar
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    Probably way off, but I'll go with old, active gelatin, my reasons are as follows:
    1: The silver nitrate solution is dumped into solution 1 rapidly (this seems consistent with old formulas?)
    2: The ripening stage seems fairly short - 60deg C for 1 hour

    Way off?
    Go on, laugh at us
    Lens caps and cable releases can become invisible at will. :D

  2. #12
    Photo Engineer's Avatar
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    Nah, I'm not laughing.

    I'm so used to modern emulsions Ben that it took me a while to read these old ones myself so I got poor results, as you cannot always tell which type they are just by reading unless you catch the signals. The people publishing love to leave out lots.

    So, it is like reading Italian for years and then trying to read Latin. There is a big difference and I had to learn that myself, as none of these old-timers are around now to tell us.

    Grant didn't give us the clues either.

    PE

  3. #13
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    One more attempt...

    This is using old (active) gelatin because cadmium chloride and the gelatin itself were components of early emulsion attempts to move away from wet plates (collodion).

    Can't lie about this; I had to dig in a few history books for this, and I could have misinterpreted the role of the cadmium. But it was worth a shot...

    Thanks,

    Bob

  4. #14
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    Bob;

    Cadmium was used up till 1970, and is not the answer.

    Thanks anyhow....

    PE

  5. #15
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    PE,

    You don't have any objections if I keep at it until someone gets it right, do you ?

    Bob

  6. #16
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    I'll probably give the answer before then.

    PE

  7. #17
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    The Answers

    Here goes with the answers:

    1. The use of Egg Albumen was certainly a hint. It was proved by the fact that there was no additional use of sulfur to sensitze the emulsion. Gelatins before about 1950 were active gelatins that added sulfur sensitization during the making process. These gelatins were used in the same era when egg albumen was commonly used. But the use of Albuemn by itslef was not proof as many still use it today for the surface characteristics it can add to a coating.

    2. The use of Magnesium Oxide or Magnesia in any formula is a hint that the formula is old. Early emulsions used non-deionized gelatin and the pH varied all over the place. Formulas added Magnesia in varying amounts (or a standard amount if your gelatin was consistant) to adjust the acidity of the gelatin. This was put in before the wash as it was usually washed away by the next step. You will see this in very old formulas as "Alkali balance or Acid balance, add Magnesia solution to balance the acid content of the gelatin as needed". That is approximately the way it appears in several old formulas that I have dating from the 30s and 40s.

    3. Salted gelatin ISO wash. Adding Sodium, Calcium or Magnesium salts particularly the Sulfate as we see here, was an early and imperfect method of washing emulsions. When PA gelatin (phthalated) became common, this method was abandoned.

    So, those were 3 hints to me, along with the unknown solution which is virtually impssible to decipher unless the destription is given somewhere in Steigman's work. I doubt Grant would leave it out if published, and if not published then it was a secret 'magic elixir' added to adjust the contrast. I have not looked it up and have not bothered Grant for more information.

    PE

  8. #18
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    haha. So I was Waaaaay off then!
    Thanks for ending the suspense anyway.
    It seems like speaking another language, with tiny little hints scattered around.
    Lens caps and cable releases can become invisible at will. :D

  9. #19
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    possible answer to Rr340?

    Quote Originally Posted by Photo Engineer View Post
    So, those were 3 hints to me, along with the unknown solution which is virtually impssible to decipher unless the destription is given somewhere in Steigman's work. I doubt Grant would leave it out if published, and if not published then it was a secret 'magic elixir' added to adjust the contrast. I have not looked it up and have not bothered Grant for more information.

    PE
    Hello PE,

    Just out of curiosity, I entered "Rr340" into the Google patent search, and it popped up in patent number 2930693, where a "Rr340" is listed as a "green sensitizing dyestuff". Could this definition of "Rr340" be a possible fit as used in this formula?

    Thanks,

    Bob M.

  10. #20
    Photo Engineer's Avatar
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    Bob;

    Yes, it might be. This is not a Kodak designation for a green sensitzing dye though. In fact, it is not a Kodak designation for any dye at all AFAIK. Therefore, if used by Grant it would be from a patent, old document or by private communication.

    The actual structure may be unknown to us then unless you can get the BIOS report referred to in the patent. For those of you unfamiliar with the BIOS reports, these are the disclosed AGFA formulas published at the end of WWII. The formula is stated in the patent to appear in report 1355 page 86.

    Under the circumstances, any green sensitizing dye might work, but I'm not familiar with the need to spectrally sensitize lith emulsions.

    PE

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