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  1. #1
    Photo Engineer's Avatar
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    Reaching the goal of a modern emulsion

    I have decided to describe emulsions in terms of 3 classes.

    The first is the "Old" or "Art" types which date from about the start of Silver Halide in Gelatin to about 1945 and are partly documented in books by Eder, Baker and Wall. They are filled with error and misdirection and also filled with myths due to the lack of science in their work. Results using these formulas can vary wildly.

    The second is "Recent" dating from about 1945 to about 1970 and these show a remarkable mix of old and new where emulsion making was undergoing a huge transition and combined old and new methods. Makes of this type can vary but are more stable batch to batch. Methods used here on "Old" emulsoins work and improve the results. In fact, some of the "Recent" formulas are "Old" formulas updated.

    The third is "Modern" which dates from about 1970 to the present day. These are typified by tightly controlled making run by computers with predictable results just about every time. The methods used to make these emulsions need their own specific equipment.

    Now, here is the problem. I can write any of these types down on paper and compare the methodology for you, and all of the above are in print (BIOS and FIAT Reports, Wall, Baker, Eder, etc), but they all lack some critical data in print or are filled with obfuscation. But, the Modern" emulsions are more clearly delineated in some recent patents. BUT - none of the modern work says anything about the means by which the emulsion is chemically sensitized or as we call it "finishing". Yes, I have found that I can make a "Modern" emulsion, but I don't know how to finish it! I was never an expert on this and did not start work on finishing until my last year at EK.

    And, searching my notes, I find that I have notes on exactly one emulsion finish given to me in preparation for design of a modeling and scaling program for the finishing process. Here is the catch. A typical modern emulsion make takes about 10 steps and up to 3 hours. A finish takes up to 30 to 40 steps with exotic coded chemistry, ramps up and down in temperature and addition of Silver Nitrate and Sodium Bromide during the process. There are also changes in pH.

    So, I have decided that one of the major barriers to achieving results close to Modern emulsions would be replicating the very confidential methods of finishing the emulsion with Sulfur, Gold, Acid, Base, Antifoggants and Heavy Metals.

    I thought you all might be interested in this line of reasoning. I find it interesting and it will probably remain a secret unless one of the experts in the field decides to come forward. I talked to one not too long ago, and he was more interested in getting a new roof on his house than discussing these types of things. I can fully understand his position, as life must go on and there is not that much interest here for the "real" nitty gritty of the emulsion making process.

    I guess that we will be stuck with Sulfur, Gold and Heat!

    PE

  2. #2
    hrst's Avatar
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    Interesting stuff. On a bit longer time scale, I would be very interested in hearing how to make those "modern" emulsions, or at least close to them. Process automation is, after all, relatively easy task. I'm just afraid this detailed know-how on finishing may disappear without being ever published in a clear form. Let's hope that won't happen.

  3. #3
    Hexavalent's Avatar
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    I'm still going to call my last batch of emulsion "modern", it IS less than three months old

    A finish takes up to 30 to 40 steps with exotic coded chemistry, ramps up and down in temperature and addition of Silver Nitrate and Sodium Bromide during the process. There are also changes in pH.
    I'm assuming that the 'finish' doesn't include the finals/doctors used for coating, preservative, anti-static etc., etc., there is still a long journey between the beaker and the shutter.
    Last edited by Hexavalent; 01-09-2012 at 09:04 AM. Click to view previous post history.
    - Ian

  4. #4
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    I got started as a photographer right at the tail end of the great Kodak products. I’ve watched one film or paper after another disappear or change characteristics so much that it should have been renamed. In all reality, Tri-X has been “discontinued” at least a couple of times. Over the years, I’ve developed the slightly cynical hypothesis that at any one time only one Kodak engineer knows how to make a product start-to-finish. It’s his baby, and by god, it’s going to the grave alongside. What possible difference should it make to a retired Kodak finish chemist if one, or a million, people are interested? I’d wager he would be keeping his ‘secret’ (should he actually know all the parts) regardless.

    Chemical photography will muddle along. Its roots are struck deep in art history. Ilford is a phenomenal company and the others coming up in the ranks are learning and improving year-by-year. On the diy front, I’m just waiting for Kirk Keyes’ beautiful little girl to get to teen age. Kirk is a superb chemist. When he gets back to emulsion making, we’ll see some real progress. Right now, I’m truly enjoying the progress hrst and hexavalent are making. Bill Winkler is my personal hero. I keep digging deeper into the literature and gleefully playing with my chemistry set. There’s a lot of info available. No reason to be pessimistic for the future. It won’t necessarily look exactly like the past, but the problem with that is…??
    Last edited by dwross; 01-09-2012 at 10:11 AM. Click to view previous post history.

  5. #5
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    Ian;

    The sequence is: Make, Wash, Finish, Spectrally Sensitize, Add Finals, Coat. Wash and Finish can be inverted in order at the expense of having less effect from the finish in terms of contrast, speed and fog.

    As for the rest, the best we are doing now are Old or "Art" emulsions with boosts in technique to bring them up to "Recent" emulsions and without any publications, this will take years to learn.

    Teams of people worked on products so that the loss of one person would not paralyze production. This happened one time, with Ektachrome Type R paper, when there was such low production there was only one engineer, and during a protracted illness, there was no production. And so, they changed that procedure for even small runners.

    With the low staffing today, IDK what goes on really.

    PE

  6. #6
    Hexavalent's Avatar
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    Thanks for the clarification of the sequence.

    Does the practice of RS (run salts) makes also mark a turning point into "modern" emulsions?
    - Ian

  7. #7
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    Yes, more or less, but until there was a practical method of control it was difficult to use. That is why I used the ~ on the dates. RS emulsions date from the mid '50s as a guess. IDK for sure but they were in use without control in the early and mid '60s.

    PE

  8. #8
    Hexavalent's Avatar
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    ... I find it interesting and it will probably remain a secret unless one of the experts in the field decides to come forward. I talked to one not too long ago, and he was more interested in getting a new roof on his house than discussing these types of things.
    ...
    PE
    I know some people who can be very "persausive"
    - Ian

  9. #9

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    When all the Kodak pensioners get their pensions turned over to PBGC, and capped at under $50,000 per year, they may get a little less loyal to their confidentiality agreements with Kodak. Maybe a lot less loyal.

    (This is a likely result if Kodak goes through Chapter 11.)

  10. #10
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    I doubt it!

    PE

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