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Thread: A real formula

  1. #51

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    Dear PE,
    I don't mean to beat a dead hourse, I realy don't! But I am cornfused! When you wrote "Adjust gelatin leval to desired 5-10%"
    You are saying : add more gelatin? Dry or in solution?
    Perhaps I did make this in class. But I have never seen such an anemic emulsion befor. By anemic, I mean soft at 33F.
    Bill

  2. #52
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    Well, Bill, under normal conditions, you should have a 5 - 10% solution of gelatin. If it takes solid gelatin, then that is what you have to add, but if not you can use up to 20% gelatin. If you use solid gelatin then heat the emulsion to 40 deg C and hold with the solid gelatin with stirring for about 1/2 hour. That will melt the gelatin and then you refilter.

    IDK how you washed it. Noodle washing dilutes emulsion. You were going to use Jim Browning's formula last I read. That is a noodle wash. So, if this is too dilute by either method, you are doing something wrong.

    PE

  3. #53
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    Please note in the OP that I suggest adjusting the gelatin to 5 - 10%. This can be done before or after the wash. It depends on method of wash and on the amount of dilution given to the original pot by the amount of ammonia used. I used household ammonia in one case and it was too dilute to set. I used 28% ammonia and it was just fine.

    There are precise notes on this formula given to my workshop students in their notes.

    PE

  4. #54

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    Thanks...now I see why film is expensive...actually, when I read the instructions above, it is remarkable that film is as inexpensive as it is. I can only imagine how difficult it is to mass produce an emulsion to exacting standards over and over again....can you tell us, briefly, how Kodak manages to make a film like TMY to such exacting standards in darkness? Thanks.

    Ed

  5. #55
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    Ed;

    Emulsions are now made in huge batches by using automated equipment. Everything is controlled to the precise flow rate, temperature, time, and mixing rate (rpms and combined flows as well as adjusting turbulence during mixing). This is done under dim red light and sometimes with IR goggles.

    Coating is done at precise rates in flow and throughput of support with carefully regulated chemicals.

    The chemistry used involves up to 9,000 ingredients or more in one color film, all of which are tested for impurities before use, and the final products are tested at every stage of the operation. The emulsion is tested before coating and the coating is tested after the emulsion is dry.

    I could go on, but only Kodak, Fuj and Ilford have the rigid specs for this fully worked out. All other companies use less rigorous methods. The one exception is the remnant of Agfa. Agfa once had the same standards and the remaining Agfa operations have been able to maintain most all of them.

    PE

  6. #56

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    Quote Originally Posted by Photo Engineer View Post
    You made it in class.
    Bill - the formula at the start of this thread is very close to what we made in class. I looked in the handout, and as I measured out all the chemicals we used, I can tell you we made the 4x Scale of the Silver Bromoiodide VHS emulsion. It's almost exactly what's posted here - we used a bit more silver in the class - look in your class formulas handout to see how much.

    The other difference between here and class is we let the one from class ripen longer than 2 hours. And we used phthalated gelatin so we could do an isowash on the emulsion in class.

    From the couple emulsions I've made, I'd suggest swelling the gelatin with a little water (try about 1 part water to 1 part gelatin) before adding it to bring the gelatin up to the 8% or so conc. The times I've added dry gelatin, it seems like it just takes longer to get it to dissolve into the pot than when I swelled it with a little water.

    Kirk

  7. #57

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    Thanks PE and Kirk,
    The reason for my making the emulsion from this thread was that I wanted to start with a "bair-bones" emulsion for optimization of of sensitizers and hardener. Yes, I can and will do that with any emulsion formula. This one just "looked" very easy. I misinterpreted.
    Thanks again,
    Bill

  8. #58
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    Bill;

    About 150+ grams of dry gelatin added any way you wish will bring the emulsion up to about the percentage you want. It is easy to calculate from the figures.

    PE

  9. #59

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    Thanks...thousands of ingredients, all tested for impurities...rather impressive I think. Did you omit some of the other manufacturers for cause, e.g., Adox, Foma, Bergger, etc.? Are the "less rigorous standards" reflected in the quality of the film? There have been occasional statements here and elsewhere about the problems with some of these films. Indeed, I know of several well known photographers who gave up using Bergger film because of the quality of the film.

  10. #60
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    I know how high the quality standards are of the companies I have mentioned. IDK about the others and so cannot comment. Except, as we see here on APUG there apparently are problems.

    PE



 

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