Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 71,840   Posts: 1,582,548   Online: 1017
      
Page 2 of 13 FirstFirst 1234567812 ... LastLast
Results 11 to 20 of 124
  1. #11
    dwross's Avatar
    Join Date
    Feb 2004
    Location
    Oregon Coast
    Shooter
    Multi Format
    Posts
    850
    Quote Originally Posted by Photo Engineer View Post
    Some additional thoughts expressed before.

    1. The book does not clearly state when active or oxidized gelatins are used for the makes. This makes speed, fog, and contrast variations difficult to evaluate, especially if you move on to the sensitization chapter.

    2. The use of colloidal Iodide in the sensitization chapter was in large part misunderstood in that day and age. The Iodide effect was a bit different than what they observed and is used today in most all Kodak emulsions, as the second step rather than at the end of the make due to the latest revised understanding. And, many emulsion makers today say that adding Iodide like this should cause renucleation, but it actually does not if the process is carried out properly.

    So, I can say that for beginners, this is a good book but rather dated with information that has changed over the years with better explanations and also I can say that this book starts out by leaving a lot of things out. Burt Carroll was a friend in my early years at Kodak, and just after he had retired. I have had a chance to discuss some of these things with him in the 70s. I think that he would write a totally different book today. I wish I had the resources to write a fully revised edition of his book.

    The accepted wisdom today is to dissolve salts in the kettle and add dry gelatin. Then stir while raising temperature. OR....
    Add dry gelatin to cold water and stir while raising temperature, then add salt. The latter method is quicker and is currently used. No ions but K, Na and NH4 are used as halide salts when making emulsions. All other positive ions in the kettle as halide salts have bad effects except for a few used at low concentration such as Cd, Cu, Hg, Ir, Os and Rh. These are listed in decreasing useful concentration and they do not work equally well in all emulsions. Cu and Hg are used mainly for toning to get warm toned emulsions.

    PE
    I am very much looking forward to the first graduate student who researches the history of gelatin with the characteristics of the myriad of brand names available at one time. Until then, for my purposes and interests in photographic emulsions as an historical process, I'm not finding the 'gelatin issue' a stumbling block.

    I would hope that Burt Carroll would write a different book today! That's the nature of science. If you wrote a revised edition, I would hope that someone would revise it 80 years from now . And each edition would be a valuable addition to the library of an historian of emulsion making. I have three editions of Fundamentals of Photographic Theory by James and Higgins. All of them have valuable information. The same is true for the four editions of The Theory of the Photographic Process, first by Mees, then by Mees and James, and finally by just James.

    'And, many emulsion makers today say that adding Iodide like this should cause renucleation, but it actually does not if the process is carried out properly.'
    That sounds like it's a book all of its own. Actually, that's the kind of opaque statement that's a pretty strong motivation to dig into the literature.

    I'll add a short note for the non-chemists who would like to join this 'book club'. Halides (at least the ones we care about) are chloride (Cl), bromide (Br), and iodide (I). They combine with potassium (K), sodium (Na) and NH4 (ammonium ion). The combinations are 'salts'. NaCl, sodium chloride, is common table salt. The halides combine with the silver in silver nitrate (AgNO3) to form silver halides, sometimes noted as AgX. The silver halide is the photosensitive constituent of the emulsion.
    Last edited by dwross; 12-09-2010 at 10:26 PM. Click to view previous post history.

  2. #12
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,530
    Images
    65
    Denise;

    To start with, if I wrote a book today (I am as you know) it probably would not be UPDATED in the future due to the lack of R&D on analog. This is a sad note.

    I spent the day at GEH with many of the people there discussing conservation issues and recreating historical processes. There is too much for one person to cover, so the history of KI added to emulsions will have to take a side line to the huge overall history of Analog, sorry to say.

    Added to the halides you mention there are Fluorine and Astatine. Now, these are not used, but why not would iin itself cover a chapter in a book as would the reasons for not using Calcium, Magnesium and other salts of halides. This is not trivial, it is more than a lifes work of many individuals. And, few are interested. This is, in part, hard core chemistry, and the early 20s is soft core in terms of today's knowledge. So, as things move forward, Phlogiston theory is forgotten.

    PE

  3. #13
    Hexavalent's Avatar
    Join Date
    Nov 2009
    Location
    Ottawa, Ontario, Canada
    Shooter
    Multi Format
    Posts
    550
    Blog Entries
    3
    Quote Originally Posted by Photo Engineer View Post
    Denise;

    Added to the halides you mention there are Fluorine and Astatine.
    PE
    Astatine: very very expensive self-exposing emulsion
    - Ian

  4. #14
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    23,530
    Images
    65
    Astatine, arrested for exposing itself!

    PE

  5. #15
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    Fascinating.... what more can you say about these exotic halides? 20 words or less will do (or more if you please!).

    It's sad that knowledge will be quite literally lost because of the way in which our culture is organized. EK & Fuji have taken the making of photographic emulsions to nearly theoretical limits of perfection, wouldn't you agree? And yet, due to corporate interests & proprietary knowledge, that information will die with these companies. When it's all said and done (like 100 years from now), will this information be accessible at all?

  6. #16
    Hexavalent's Avatar
    Join Date
    Nov 2009
    Location
    Ottawa, Ontario, Canada
    Shooter
    Multi Format
    Posts
    550
    Blog Entries
    3
    Astatine is a radioactive halogen with a short half-life (hours). Extremely rare, expensive and unstable.
    AgF is very water soluble, unlike the 'other' Silver halides, and is a bit too reactive to be useful.

    More than 20 words, and probably worth less than 2 cents
    - Ian

  7. #17
    holmburgers's Avatar
    Join Date
    Aug 2009
    Location
    Rochester NY (native KS)
    Shooter
    Multi Format
    Posts
    4,423
    Images
    2
    Not at all, very interesting!

    Quote, "Astatine is currently the rarest naturally occurring element, with less than 30 grams estimated to be contained in the entire Earth's crust."

  8. #18
    dwross's Avatar
    Join Date
    Feb 2004
    Location
    Oregon Coast
    Shooter
    Multi Format
    Posts
    850
    Quote Originally Posted by holmburgers View Post
    Fascinating.... what more can you say about these exotic halides? 20 words or less will do (or more if you please!).

    It's sad that knowledge will be quite literally lost because of the way in which our culture is organized. EK & Fuji have taken the making of photographic emulsions to nearly theoretical limits of perfection, wouldn't you agree? And yet, due to corporate interests & proprietary knowledge, that information will die with these companies. When it's all said and done (like 100 years from now), will this information be accessible at all?
    Your last question is really two separate questions. "This information" is neither homogeneous nor linear. Silver gelatin photography covers 130 years (and counting) of science, art, and technology. The high-tech end of the timeline is almost certainly safe. Kodak's failure of vision is probably the best thing that could have happened to analog photography. Other companies can finally get their feet in the door. George Eastman was secretive and monopolistic in the extreme. The corporate environment he fostered was semi-loony. Secrets for the sake of secrets. A good example of that mindset can be seen today in the Wikileaks broohaa. Why in the world was most of that junk secret?

    Anyway, Ilford seems committed to silver, and the Eastern European and Chinese companies are really coming into their own. I don't see them going away, at least in the aggregate.

    What may be endangered is handcrafted silver gelatin. It was never actually a handmade product for more than about ten years. And here's the important point: It was totally commercial propaganda that convinced photographers that they could no longer make their own materials -- and propaganda became fact. After about 50 years of technological advancement, it was true that the home darkroom could no longer make the same products as Kodak, but that still leaves a lot of great recipes available to us, each with a distinctive beauty and the satisfaction of the handcrafted product.

    The next thing here is hard to say, or at least to say without butting heads with a couple of regulars to this forum. If we want to learn to recreate excellent emulsions, those within our technological reach as handcrafters, we absolutely can. But, it will take staying focused and on point. There are only three halides important to photography. Discussing the others, or pretending that understanding their chemistry and physics is even remotely necessary to making an emulsion, is nothing but a meaningless digression. 'Soft core' chemistry is more than good enough to make gorgeous emulsions. I am not a chemist, and I'm printing a portfolio right now that has me proud-to-busting. If you're really interested in making emulsions, please don't be discouraged or deflected by the nay-sayers and pessimists.

  9. #19

    Join Date
    Apr 2005
    Location
    San Bernardino, CA
    Shooter
    8x10 Format
    Posts
    749
    Surely (?), EK and the other major players in emulsion research have kept records of all formulas and other aspects of their research. Although they will not release these records in the foreseeable future,100 years from now they may be made available to those interested. I hope that these companies don't behave like a Government and burn all the evidence.
    There is hope for analog. A giant solar flair could take out all the circuit boards in the world, sending us all back to 1850.
    Today,I will read Chapter II. I have nothing better to do.
    Bill
    Bill

  10. #20

    Join Date
    Apr 2005
    Location
    San Bernardino, CA
    Shooter
    8x10 Format
    Posts
    749
    "Knowledge is Power",only if it is exclusive!

Page 2 of 13 FirstFirst 1234567812 ... LastLast


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin