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  1. #1

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    Photographic Emulsion Stabliizers

    Here's something I ran across on Google Books:
    http://books.google.com/books?id=CPm...&hl=en#PPP1,M1

    It looks like about half of the book is there.

    Kirk

  2. #2

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    This book is actually pretty good, but it is also highly advanced for most amateur emulsion makers.

    Birr also wrote a book on emulsion stabilizers, but his book is more like collection of quotes from others' work. Fischer's book is more consolidated knowledge in expository style.

    However, Fischer often stops at description of the chemical compound, and does not get into why this compound is better than others for a particular application, etc. Those are left for the reader to find out elsewhere, and for that matter, I don't know of a good single book to recommend.

  3. #3

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    Incidentally, I use the following to stabilize my emulsions:

    KBr
    4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene
    1-phenyl-5-mercaptotetrazole
    2-mercaptobenzimidazole
    6-nitrobenzimidazole
    5-methylbenzotriazole
    nucleic acids

    You might want to look these up in Fischer's book. If you are shopping for chemicals, I listed them roughly in the order from the most essential to optional.

    It may also be of interest to note that, in recent practice, chemical digestion is often carried out in presence of agents that enhance the reaction yield, so as to minimize the amount of excess agents when the optimal sensitivity is obtained. This makes the emulsion performance more stable over the course of shelf life. (For example, in traditional technique of sulfur sensitization, thiosulfate is added to the emulsion and then the emulsion heated for so many minutes. In this scenario, only a small fraction of thiosulfate is used to make effective sulfur sensitization center, and the excess can slowly react to increase fog and drop speed over the course of storage period. If you have a way to obtain the optimal speed with more complete reaction yield, and then start with less sensitizer, then less excess reagent will result, and that's a much better strategy.)

  4. #4

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    Ryuji - could you give a list of sources that we can obtain these from and appoximate costs?

    KBr is a non-issue, but some of these others are rather obscure chemicals for a lot of people.

    I've found 1-Phenyl-5-mercapto-1234-tetrazole at artchemicals for $36 for 5g:
    http://www.artchemicals.com/1-Phenyl...37051C585.aspx

    Any suggestions on the rest?

  5. #5

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    These compounds are rather easily available from scientific chemical supply houses, although their price is high. (But we are buying such a small qty anyway)

    I'll list common acronyms to facilitate discussion.

    TAI: 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene
    PMT: 1-phenyl-5-mercaptotetrazole
    2-MBI: 2-mercaptobenzimidazole
    6-NBI: 6-nitrobenzimidazole
    MBTA: 5-methylbenzotriazole

    TAI is used in a relatively large quantity, 100-1500mg per mole silver. Other compounds are used very small quantities, like 1-50mg per mole silver.

    MBI is widely available and it is cheap, but like above, it is used in such a small qty.

    NBI is not that essential. MBTA is also very common for color emulsions but not that essential.

    I started my emulsion making with KBr, PMT and TAI. These are definitely the most often used stabilizer cocktail.

    Nucleic acids are not a single compound. You may find a mixed nucleic acids or partial RNA hydrolysis products. Or you might look into individual ones. These are used only in advanced formulas. Not that essential.

  6. #6

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    I should also note that, these compounds, particularly TAI and PMT have some other names for the same compound. You also want to search by aliases and CAS number.

    If your goal is a good plate emulsion, TAI is pretty important.

    If your goal is to make chlorobromide or chloride printing emulsion, PMT is pretty important.

    Also, plain old benzotriazole (a.k.a. 1H-benzotriazole or 1,2,3-benzotriazole) is usable at a somewhat increased quantity (like 30-300mg per mole silver) but not as effectively. Definitely better than not using any, tho.

  7. #7

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    Thanks - that helps narrow the list a bit.

  8. #8

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    I'll definitely get some TAI and PMT (I've got a bit now, but no stocks for long term).

    I notice that Jim Browning's dye matix fomula uses not only Potassium Bromide and 7-Hydroxy-5-Methyl-1, 3,4-triazaindolizine (a variation of TAI I assume), and 1-Phenyl-5-Mercapto Tetrazol (PMT), but he also adds Manganous Sulfate and Sodium Azide.

    Care to comment on the Manganous Sulfate and the NaZ?

  9. #9
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    reference regarding Sodium Azide (which is an explosive):

    http://www.apug.org/forums/forum205/...trix-film.html

    Bob M.

  10. #10

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    Bob - That thread was pretty lean on info on why and how one would use sodium azide as a stabilizer. Seems like it broke down into a dry transfer vs. who knows what the hell thread a couple of times. It was downright painful to read at times. I even saw your name in there as it was disintegrating...

    Any other suggestions?

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