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Thread: A real formula

  1. #71
    EASmithV's Avatar
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    Do you have any examples to show? I'm interested in seeing what the grain is like. One would think that a slower film would have better grain... but having used copy film I know better.

  2. #72
    Photo Engineer's Avatar
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    Quote Originally Posted by EASmithV View Post
    Do you have any examples to show? I'm interested in seeing what the grain is like. One would think that a slower film would have better grain... but having used copy film I know better.
    I have posted quite a few here, and at the risk of using up Sean's storage space, I guess I can do it again. Left is an ortho sensitive version of the emulsion in the OP, using PA gelatin and ISO washing. The sensitizer was Erythrosine. The right image is a Scanning Electron Micrograph of the emulsion. The results in this case are independant of whether Dye is added or regular or ISO washing is done. I have checked them out with SEMs also.

    PE
    Attached Thumbnails Attached Thumbnails glass plate 3 ISO 40 resize pos scan.jpg   Electron  micrograph - BrI SRAD.jpg  

  3. #73

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    PE, everything have been fine, as you said I just added the gelatin before washing few days ago, not a big deal , now I m waiting for time to try the 4 4x5 glass plate I coat with Osterman's method (I also do Wet plate).
    I m very busy at work nowadays but hope to sho few samples in the next days

    Ok I did a few test just to know, and my emulsion is completly foggy, I hope it comes from the drying box I use (color paper transporting box to RA4 developping machine), but I m not sure maybe the whole batch is over, I m using a yellow light and I hope it will not come from that, I will give another try in better condition.

    By the way, what are your recommandation for processing this emulsion ? I used a paper developper (Agfa Neutol) at 1+4 because I add problem with ID11 (peeling in the fix bath), I used to make my own but had not enough component for now so ..
    Last edited by efranqueville; 01-18-2009 at 03:12 PM. Click to view previous post history.

  4. #74

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    I made my first emulsion in a long while last nigth, using this formula, and I have a couple of questions:

    1. when I diluted the AgNO3 with Ammonia, it turned brown, as I expected, and as I added more, it turned darker and darker until it cleared up, leaving a brown precipitate at the bottom. The precipitate looked suspiciously like silver. Is this normal, or do I need to get a different bottle of ammonia?

    2. My hot plate is in capable of holding a temperature under 130 degrees F. what effect on crystal growth will this have?

    3. even in a chilled ice bath, my noodle wash caused an increase in volume, about 10-15%, using about 8% gelatin. The resulting emulsion afterwards was not terribly stiff (Bloom 250 photo grade gelatin). Is there a temperature at which photo gelatin breaks down?

    Thanks for the help.

  5. #75
    Photo Engineer's Avatar
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    Here are some answers:

    1. If there is a brown or black ppt at the bottom there may be 2 causes. One is not enough ammonia and the other is that the Silver Nitrate is old or low quality. If adding more ammonia does not clear up the brown ppt. then the Silver Nitrate is not very good.

    2. As temperature goes up, crystal size, fog and speed generally go up. You can offset this by shorter hold times at a given temperature in some cases. As temperature goes down, the crystals go down in size, fog and speed decrease.

    3. I use 4 deg C for my wash. Volume generally goes up. You can add some 20% gelatin to this to stiffen it up, but you usually have to coat a tad more emulsion per unit area to offset the dilution.

    Gelatin can break down at any temperature if the pH is too high or low and it can break down at any temperature with a long enough hold time. I try to stay below 80 C and preferrably at or below 60 C for these makes. I try to keep holds at or below 1 hour and the Ammonia digest is probably not alkaline enough to cause a probem with these conditions.

    PE

  6. #76
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    Quote Originally Posted by Photo Engineer View Post
    Silver halide is sensitized by adding thiosulfate at 1 - 100 grams / mole of silver present. Unfortunately, this level is based on grain size (surface area actually) and therefore unless you have electron micrographs you have to determine it by trial and error.

    Gold is used a 1 part of gold salt / 3 parts of thiosulfate.

    Don't use Dichromate.

    PE
    As a very kind person has noted, this post should read Thiosulfate is added at the rate of 1 - 100 mg / mole of Silver present. And it is based on Sodkum Thiosulfate Pentahydrate.

    Sorry for this mixup.

    PE

  7. #77
    kb3lms's Avatar
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    Add 28% ammonium hydroxide to B with stirring until a clear solution results.
    PE,

    At this point, how much ammonium hydroxide is used? I am ordering materials from the Formulary and want to make sure I get enough. Would I be correct in understanding that it is a fairly small amount?

    Thanks!

  8. #78
    hrst's Avatar
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    For me, it was around 20% of solution B volume.

  9. #79
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    Quote Originally Posted by kb3lms View Post
    PE,

    At this point, how much ammonium hydroxide is used? I am ordering materials from the Formulary and want to make sure I get enough. Would I be correct in understanding that it is a fairly small amount?

    Thanks!
    It really depends on batch size.

    I use about 25 ml of 28% Ammonium Hydroxide for about 250 ml of emulsion, but this depends on quite a few things such as the "real" concentration of the Ammonia solution. It is subject to changes due to evaporation of NH3 gas. So, I order about 250 ml at a time and it lasts me for about 5 - 10 batches depending.

    PE

  10. #80
    kb3lms's Avatar
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    Thank you for the info. Well, I have off between Christmas and New Year's so I am looking forward to making my first run soon!

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