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  1. #1
    kb3lms's Avatar
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    Bromides of Various Sorts

    Since I am usually (and sometimes foolishly) not of the faint-of-heart in these things, I throw out the following as a thread starter. I hope others can contribute.

    What are your thoughts on Potassium Bromide (KBr) vs Ammonium Bromide (NH4Br) vs Sodium Bromide (NaBr) as a source of Bromide ions for precipitation?

    I've only used KBr myself as that is what I have in my shop, but have seen recipes/formulas using all three variations.

    -- Jason
    All this has happened before, and all this will happen again.

  2. #2
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    Unfortunately, this is the kind of topic that so often turns acrimonious here. There was a thread not too long ago that asserted ammonium bromide was a "crutch". Could never figure out why (except maybe because it works so well in an emulsion??) Anyway, no substantiation to the claim. Just an assertion.

    Jason, perhaps the best way for you to answer the question is to try different bromides. You know where to find a proven ammonium recipe . http://thelightfarm.com/cgi-bin/html...tent=15Jun2013.

    I, in turn, will refrain from speculation on sodium bromide, as I haven't yet tried it. It's the real paradox of these kinds of discussions. It is natural to want to speculate, but it really serves no purpose. So, you are left with people who have actual experience, and in our case, there aren't that many emulsion makers yet. There wouldn't be much of a discussion among the few of us, but we can hope and encourage others to take the plunge.
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    kb3lms's Avatar
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    True, it does. Well the thread can be deleted if the moderators like. I was hoping others would contribute in a positive sense.

    In the near future, I do plan to try other bromides as well as a reduction or even elimination of ammonia.

    My hope was potting it on the front page "above the fold" might get some activity again.

    Your recent articles on "The Light Farm" are excellent.
    All this has happened before, and all this will happen again.

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    MDR
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    You forgot Cadmium, Lithium, etc Bromide I believe that the choice of bromide somewhat influences the lifespan and contrast of the emulsion this is at least the case in the wetplate world. Cadmium was the preferred Bromide because of the keeping qualities of the emulsions. Ammonium ads a little speed but lowers the lifespan of the emulsion. Sodium and Potassium Bromide should be about equal at least according to older literature. It's also important to know where the formulas were created for example German formulas (Agfa) liked their potassium bromide because it was readily available. Economy does play a role in the choice of ingredients.

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    Quote Originally Posted by dwross View Post
    Unfortunately, this is the kind of topic that so often turns acrimonious here. There was a thread not too long ago that asserted ammonium bromide was a "crutch". Could never figure out why (except maybe because it works so well in an emulsion??) Anyway, no substantiation to the claim. Just an assertion.

    Jason, perhaps the best way for you to answer the question is to try different bromides. You know where to find a proven ammonium recipe . http://thelightfarm.com/cgi-bin/html...tent=15Jun2013.

    I, in turn, will refrain from speculation on sodium bromide, as I haven't yet tried it. It's the real paradox of these kinds of discussions. It is natural to want to speculate, but it really serves no purpose. So, you are left with people who have actual experience, and in our case, there aren't that many emulsion makers yet. There wouldn't be much of a discussion among the few of us, but we can hope and encourage others to take the plunge.


    Here we go again. The effects of ammonium ions in an emulsion have been documented, and discussed ad-nauseum here. Ammonium is a silver solvent, and as such changes the growth rate and morphology of halide crystal. The use of ammonium is a short-cut method compared to controlled crystal growth. That being said, it's probably quite sufficient for most home-brew emulsions.

    Should you want to explore the role of different halide salts in the precipitation, solubility and effects upon vAg will be revealing. That route is however a 'technical' approach - some prefer the "just because" explanation.

    I would be pleased to provide further detail off-list.
    - Ian

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    dwross's Avatar
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    Alas, yes. Here we go again. But here's the thing. We can break this ugly cycle, especially if we move in the direction of showing our work. I'm a retired scientist. Love the geeky stuff and never met a piece of lab equipment I didn't drool over. But, please, you have to admit that fancy labs for simple emulsions is more about G.A.S. (as often as not itself a procrastination tool) than quality. And isn't this forum about home-brew emulsions? And art?

    Back to the suggestion we show work. A print or negative in hand is not a "just because" explanation. It is a physical object. That object is likely the reason most people here would want to make their own emulsions.

    Some people will be interested in the physics and chemistry of the object. Others will just want to create. Some of us crave both. It's all good. You don't have to understand the Krebs cycle in yeast to bake a wonderful loaf of bread, although I think understanding that the yeast is there so that you get a loaf and not a tortilla is a handy thing to understand. I hope that seems a reasonable analogy to emulsion making.

    One more thing: If we say we can't talk about things that have already been talked about here, then we might as well turn off the lights and lock the door .
    Last edited by dwross; 10-14-2013 at 02:19 PM. Click to view previous post history.
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    dwross's Avatar
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    Quote Originally Posted by MDR View Post
    You forgot Cadmium, Lithium, etc Bromide I believe that the choice of bromide somewhat influences the lifespan and contrast of the emulsion this is at least the case in the wetplate world. Cadmium was the preferred Bromide because of the keeping qualities of the emulsions. Ammonium ads a little speed but lowers the lifespan of the emulsion. Sodium and Potassium Bromide should be about equal at least according to older literature. It's also important to know where the formulas were created for example German formulas (Agfa) liked their potassium bromide because it was readily available. Economy does play a role in the choice of ingredients.
    I've been trying to think of ways that 'interested-but-not-ready-just-yet' people can participate in the discussions. You've given me an idea. I have no idea if it has legs, but it might be worth a try.

    Everyone has access to the older literature. Maybe a real book, or more likely the internet. Maybe we could share interesting facts, quotes, and history. I had no idea cadmium was preferred for its keeping qualities. I wonder if that's also true for silver gelatin emulsions. What I know about relates to emulsion color and characteristic curve control.

    The only potential downside I can think of is that this might turn into dueling references. Cross that bridge if and when necessary. Fingers crossed.
    www.thelightfarm.com
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  8. #8
    MDR
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    Denise pure Potassium formulas usually clears a lot faster than cadmium emulsion the later has a longer shelf life and some people think clearer/cleaner look. Josef Maria Eder has a book about gelatine (bromide and chloride) emulsions that is part of his Ausführliches Handbuch der Photographie https://ia700306.us.archive.org/14/i...05edergoog.pdf and https://ia600302.us.archive.org/4/it...06edergoog.pdf
    unfortunately they are in German but still interesting

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    kb3lms's Avatar
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    Well, I can wade through a little German (welcome to the Pennsylvania Dutch Country ).

    Once I had read about Cadmium being used in paper emulsions because of keeping AND tonality. How is Cadmium Bromide used? Does one use it like KI (a small mole percentage) or use it in place of Potassium (or other) Bromide?

    -- Jason

    PS: I threw this topic out as a thread starter. Been dying for an emulsion discussion of any sort. I have NO agenda as to where this thread goes and no need for any matches of any sort.

    PPS: Denise, good idea on the quotes and passages. I'll see what I might find.
    All this has happened before, and all this will happen again.

  10. #10
    dwross's Avatar
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    One of my favorite books is the SPSE Handbook of Photographic Science and Engineering, edited by Woodlief Thomas, 1973. In fact, in a pinch, I could probably get by with just it and Baker's book. It's not 'almost free' like it was until recently, but it's still really cheap as these things go. Here's the page this morning from Abebooks (a site well worth bookmarking.) http://www.abebooks.com/servlet/Sear...ographic&sts=t

    The book has a chapter on "Silver Halide Emulsions" that has a number of recipes that were test emulsions at the Kodak research labs. Two of them have cadmium chloride in their formulas. I'll just include the ingredients here, but the making instructions are short and clear. Also, the recipes scale down perfectly. The cadmium amounts are very similar to KI (potassium iodide) amounts used in other recipes. I should say that I have made both these recipes without the cadmium and they turned out very nicely. The projection paper will be in an upcoming TLF tutorial. I don't know what the cadmium would do to the emulsion (color-wise or curve.)

    Steigmann General Chloride Test Emulsion Formula

    Part I: Cold distilled or deionized water (at 5 to 10C) ..... 840 ml
    Gelatin, photographic quality ..... 30g
    Allow to soak 30 min, warm to solution, and add:
    Sodium chloride, AR ..... 15 g
    Cadmium chloride, AR ..... 0.5 g
    Citric Acid, anhydrous AR ..... 6 g
    Potassium bromide, AR ..... 0.5 g
    Part II: Distilled or deionized water ..... 200 ml
    Silver nitrate, AR ..... 30 g
    Part III: Gelatin, photographic ..... 100 g

    Chloro-Bromide Projection Paper Emulsion Formula
    (abbreviated by dwr)

    For 25 g silver nitrate, use
    Sodium chloride ..... 9 g
    Potassium bromide ..... 8.7 g
    Cadmium chloride ..... 0.5 g
    Cirtic acid, 20% solution ..... 1 ml
    Last edited by dwross; 10-15-2013 at 08:10 AM. Click to view previous post history.
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

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