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  1. #41

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    Google Books tries to apply the copyright laws of your location to limit what you can see. In the US you can see anything published before 1923 (as some wag suggested, the definition of the public domain in US copyright law may be connected to the corporate interests of Disney, and the fact Mickey Mouse was invented in 1928). In Australia, where I am, you should be able to see anything published before 1955, provided the author also died before 1955. Unfortunately, however, Google isn't clever enough to realize that Carey Lea died in 1897, and as a result they seem to apply some sort of more restrictive limit, which means I have never seen more than a snippet of anything after about 1870. This means I also can't see Kirk's Google Book references, for reasons probably similar to what Ray is experiencing in Japan.

    Google Patents doesn't seem to have any of the same restrictions and is very useful, especially for the PDFs of tables that some of the other patent sites which seem to scramble. The patent David Goldfarb referred to earlier, which connects what seems to be Polaroid Type 55 with Panatomic-X or a similar emulsion is accessible, if you go to http://www.google.com/patents and search for US Patent 3345166.

    My interest in colloidal silver for diffusion transfer receiver physical development nuclei was mainly as a safer option to heavy metals like lead sulfide. However for all the experimenting I'm likely to do it sounds like it's easier just to use fixed out paper or film. Land reproduced examples using plain paper in his Pioneers of Photography article, but I couldn't get it to work.

    However, colloidal silver might also be useful for a monobath derived from Barnes and Johnston's US patent 3392019 for "viscous silver halide photographic monobath solutions". They say "Although the particle size is not particularly important to the operation of our monobath, the particles preferably have a average diameter of 7-2,500 A." With only 0.2g Carey Lea silver, their Example 6 formula reduces the thiosulfate to only 25g/liter to develop a low speed fine grain chlorobromide emulsion at 125 degrees F in 15 seconds. Whether something similar is possible without their preferred amine is difficult to say. I didn't really understand the comparisons they make in the patent between different amines and sodium hydroxide and sodium carbonate.

    I managed to find what appears to be the dextrine method of making Carey Lea silver from J.W. Mellor, A Comprehensive Treatise on Inorganic and Theoretical Chemistry, 1923, v.3, p.561: "40 grms. of sodium hydroxide and the same amount of ordinary brown dextrine are dissolved in 2 litres of water, and a soln. of 28 grms. of silver nitrate in a little water is gradually added. The resulting liquid is clear and black, although it contains less than one per cent. of silver. On dilution, the soln. becomes red, and with further dilution, it forms a yellow solution."

    Perhaps following this you can make some sort of stock solution which could go straight into a monobath formula without any need for a centrifuge.

    Following on from Struan's comments about color, and the collodidal size of noble metals, Mike Ware's work on the new chrysotype process might be of interest.

    Sorry to be dropping in and out of this discussion. I haven't had time to do any more experimenting but was wondering about using photographic paper rather than film for the diffusion transfer. This would at least allow you to work a bit more comfortably in the darkroom. The dark red safelight I have for ortho film is very dim, and there is no way I'd want to try panchro materials in full darkness without some device like the rails Photo Engineer mentioned.

    Thanks too for your comments about contact for the diffusion transfer sandwich. I didn't realize this was yet another variable, but it makes sense. I had some images that were nearly a neutral gray, brick red, and even a purple. Colloidal silver can be an interesting material!

  2. #42

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    ON google and non-US locations? COuld you guys try one of those "anonymizer" free-web proxy sites like www.anonymizer.com and see if that works?

  3. #43

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    Yeah - google tries not to let you see anything your local government doesn't want you to see. Like you'll never see a photo of the guy standing in front of the tank in Tiennamen (sp?) Square while you are in China through google... I understand why the do it, but it just seems wrong somehow...

  4. #44

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    Truth and Knowledge

    Quote Originally Posted by Kirk Keyes View Post
    Yeah - google tries not to let you see anything your local government doesn't want you to see. Like you'll never see a photo of the guy standing in front of the tank in Tiennamen (sp?) Square while you are in China through google... I understand why the[y] do it, but it just seems wrong somehow...
    Knowledge and Truth are like anything of immense value -
    They Know No Freedom!

    Ray Rogers

  5. #45
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    Ahhh, but there is no pravda in izvestia and no izvestia in pravda.

    PE

  6. #46

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    Quote Originally Posted by Struan Gray View Post
    Interference colours can be very intense and pure, but they generally only work over a limited range of angles. Exceptions exist which work over wider angles - the canonical example is the pure blue of the Morpho butterfly wing - but as I understand it Lippmann emulsions only display their correct colours when viewed head-on.
    Yes, Lippmann photos can be viewed over a very narrow angle only.
    Reflection holograms in contrast may have huge (~180°) viewing angles. Depending on the recording material bandwidth of these „interference colors“ may vary from very narrow (< 1nm) to very broad (> 200nm).

    Quote Originally Posted by Struan Gray View Post
    Final point: the early colour I was thinking of was bare AgCl on a paper support, as used by spectroscopists to investigate projected solar and other spectra by measuring the pyrolitic or photolitic darkening of the halide when exposed to a spectrum from a prism. Herschel reports on some of these colours in his huge catch-all paper in the Royal Society's Phil. Trans. from 1840 (the same paper where he reports the use of "hyposulphites" as a fixer), but I am sure many other early workers noticed and commented upon them. These are unlikely to be caused by an interference effect, and are most likely plasmonic colours.
    That might be an interesting explanation to that old problem of natural color photography. I am referring to the discoveries/observations by Seebeck, Niepce, Herschel, Talbot, Becquerel, Poitevin, Zenker, Lippmann, Valenta...

  7. #47
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    More information on making colloidal silver after some reading of notes and etc.

    Here are the steps in making colloidal silver (photograde)

    1. Add alkali solution (NaOH) to silver nitrate or vice versa depending on the type of Silver Hydroxide you wish to form.

    2. Wash well to remove as much alkali as possible.

    3. Disperse the AgOH in water + gelatin mixing completely. Adjust pH according to the needs in step #4.

    4. Add a mild reducing agent such as Dextrin, Ascorbic acid, or Stannous Chloride.

    5. Wash to remove all trace of reducing agent and test to make sure there is no Silver Hydroxide remaining. (CRITICAL STEP)

    Selection of addition order, concentrations and type of reducing agent will influence the color of the colloid as described above. Washing after the first step is usually done on the "mud" using a centrifuge or centrifugal spiral filtrator. These are very expensive but are usually used industrially instead of the typical spinning centrifuge.

    I hope this gives more information. The specific formulas are so wide in variety that one formula will not suffice for all. I only have formulas for 2 of them. None can be applied to B&W photography.

    PE

  8. #48
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    We just don't have discussions like this anymore!

  9. #49
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    We can always try. To that goal, I'll start a new thread. I hope I'm not the only one. It would be fun and satisfying to have a number of good discussions going at once. Maybe we can attract back the good heads among us. Kirk Keyes, where are you?
    Last edited by dwross; 12-08-2010 at 04:31 PM. Click to view previous post history.

  10. #50
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    I hope I can keep up

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