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  1. #111
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    Best wishes Bill;

    Some comments might be of interest.

    Formalin usually causes an increase in fog. It is a reducing agent. Formalin may be reducing defects due to some surfactant property or just by dilution and lowering viscosity. Or it may slightly increase viscosity at the edges of defects and pull them together through a change in surface tension.

    Anyhow, just thoughts.

    PE

  2. #112

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    Yes PE,
    The Formalin vs. fog thing is a mystery. Maybe the surface tension change you mentiond might somehow inhibit foging. I just DK.
    I test my emulsions for fog by developing in D19. This developer is an agressive, high contrast developer and will usualy produce more fog than other developers.
    BILL

  3. #113
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    That is a good test Bill. If there is fog, D19 will show it up.

    PE

  4. #114
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    Here are some recent resources I've found regarding spectral sensitizing, from the holography folks.

    http://holoforum.org/forum/viewtopic.php?f=9&t=494
    http://holoforum.org/oldforum/viewtopic.php?f=2&t=6540
    http://holoforum.org/oldforum/viewto...d1e5f1831248b9

    Apparently these are sensitizing dyes as well. Possibly very expensive(?, not sure...)
    http://www.organica.de/en/Products/49,Functional_Dyes

    Very interesting opportunity to get pinacyanol chloride
    http://www.9000shops.com/holodye/index.html

    via Jeff Blyth
    http://cabd0.tripod.com/holograms/index.html

    And haven't even read this, but it looks interesting...
    The Action of Optical Sensitizers on the Photographic Plate, G. Kornfeld. Kodak Research Laboratories, Rochester, New York. Received May 25, 1938.
    http://www.nap.edu/openbook.php?record_id=9565&page=97

  5. #115
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    Umut,

    When you reference "original...technology", what era of emulsion making are you thinking of? In the beginning, there was no sensitization. That was followed by red food coloring, and then a fast-moving wave of chemicals that came and went -- with slight variations among Kodak, Ilford, and Agfa. (Fuji: I don't know much about.) Anyway, I don't think procuring sensitizing chemistry that would have been familiar to emulsion makers in the 1920s is much of a problem. I'm using a number of them.

    d
    www.thelightfarm.com
    Dedicated to Handmade Silver Gelatin Paper, Film, and Dry Plates.

  6. #116
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    Denise, would you be interested in a spectrosensitometer? Bill? That is... if I theoretically had one to offer?

    I really do think that such an instrument could be cobbled together with a little bit of effort. This might be a project that I'd be able to work on in the relatively near future (winter). I'm thinking about something made out of foam-core to begin with, but a prototype could lead to something made of wood.

    It might not be perfect, but I think it might be more useful and easier to interpret than shots of color charts.

    If there's any interest on that front, let's discuss it over here -> http://www.apug.org/forums/forum205/...sitometer.html
    If you are the big tree, we are the small axe

  7. #117
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    Oh, just try Tennessee Eastman. I believe that they sell some of these.

    PE

  8. #118
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    Quote Originally Posted by Mustafa Umut Sarac View Post
    PE , What is the molecular formula of 6,6 diethoxy 1,1 diethyl 2,4 dimethyl 2,4 carbocyanine iodide ?

    Umut
    Umut;

    It would take me a while to work out the structure, and I doubt if it would do anyone any good.

    As for providing R/G/B sensitivity, we do have dyes already posted here that do the trick and so I have no concern about it being a problem. Except for the cost, these dyes are available.

    Now, as to their working, some dyes work and some do not on any given emulson. I have 5 or 6 dyes that I tried and got 2 that work on all emulsions, but one is weak and the other sensitizes at a long green wavelength. Another one only works well on bromide emulsions as a green but works on bromo / iodide emulsions as either a red or green. This dye has been the subject of much discussion here.

    So, I cannot answer your question about "solving the problem" until I did an experiment with at least 3 emulsions with each dye. You can see how time consuming and expensive that will be. I've already done the ones about, 6 or 7 dyes with 3 emulsions and have published the good results either here or in the book.

    PE

  9. #119
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    Quote Originally Posted by Mustafa Umut Sarac View Post
    Attachment 52697CB4433150
    Chemical Name: CRYPTOCYANINE
    Molecular Formula: C25H25IN2
    Formula Weight: 480.38
    CAS No.: 4727-50-8 ....
    Ok, here we go, a proof of concept... $52/gram, minimum order of $100.

    http://chemicals.citychemical.com/it...origin=keyword

    Now, of course there's a lot more to consider here, like Ron says, but with a little effort and creativity I think we can find sensitizers that won't break the bank, hopefully one that does a good job with red.

    Umut, awesome job. However, is it necessary to copy and paste all of that?!
    If you are the big tree, we are the small axe

  10. #120
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    I got some cryptocyanine from Sigma-Aldrich 1½ years ago, the price was 43 EUR (about 55 USD) for 250 mg. As you might guess, I haven't got time to test it.

    So, that one looks quite a bit more attractive, given the much lower price and the fact that buying from Sigma-Aldrich may not be very straightforward (at least you need a company).



 

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