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  1. #11
    Photo Engineer's Avatar
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    Quote Originally Posted by DannL View Post
    Oh well, I got that info from a publication describing a kodak film. It sounded good at the time. I should have known better.
    Dont worry. I was kinda tongue in cheek.

    Sorry.

    There is little or no silver in film. It is 99.999+% Silver halide with some sulfides present and other silver salts. Any silver metal is there as a latent image if the film is exposed and that is quite resistant to oxidation. The latent image is in very low concentration and can fade with time as well.

    I shield all of my film from Kryptonite radiation!

    The Van Allen belt created by the magnetic field of the earth does a good job off keeping the sun's radiation away, but a poorer job with the higher energy of the cosmic background radiation. Much of the sun's radiation is in the form of neutrinos that go right through us and our film with no harm being done whatsoever.

    The bottom line is that there is no easy way to preserve film from heat and radiation effects.

    PE

  2. #12
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    Stockpile slow film.

    It is less sensitive to all the nasties. By using the required low exposure index and blasting the film with photons, the ratio of photon exposure to cosmic ray exposure favors the latent image.

  3. #13
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    Quote Originally Posted by ic-racer View Post
    Stockpile slow film.
    Even better: Stockpile developed film. It does not fog!

    Steve
    Warning!! Handling a Hasselblad can be harmful to your financial well being!

    Nothing beats a great piece of glass!

    I leave the digital work for the urologists and proctologists.

  4. #14

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    Outer Space is not the only sources of radiation. Since no one has mentioned it, the Earth itself is a source as well. Or your house. Or your granite counter tops.

    Depending on where you live, the bedrock or the soil under your house can give of radiation or radon gas, which is radioactive as well. If your house is made of rock or bricks, it will likely be more radioactive than a house made of wood.

    And the bit about granite countertops - I was talking with the state radiation officer a few months ago, and he was saying that some agencies are investigating measure granite counter tops to make sure the amout of radiation they release it safe. He found it interesting as granite, being a natural product, did not typically fall under his sphere of concern. He said granite is typically not a big issue, but he said the veins of red that are found in some granites are the areas of interest and much more radioactive than typical granite.
    Kirk

    For up from the ashes, up from the ashes, grow the roses of success!

  5. #15
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    Isn't there any way film can be stored to reduce its exposure to fogging radiation? I have often wondered if a block of ice and metal layers surrounding the film (water/lead layers are used as a radiation shield in nuclear plants) or even storage in a hefty metal box would help Delta 3200 and HP5 keep longer. Of course, I am talking about building a dedicated storage unit here...probably converted from a commercial top-loading freezer. I am dreading the day when fast films disappear...gotta plan ahead!
    Last edited by 2F/2F; 06-11-2009 at 07:42 PM. Click to view previous post history.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

    - Rob Tyner (1944 - 1991)

  6. #16

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    There are far more relevant things to worry about, at least until the next "significant" galactic gamma ray burst hits us, which happens on average about every billion years.

  7. #17
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    I just remembered "squiggle", as we called it in the plant. It is "linear attenuation coefficient". Every potential shield material has one for each type of EM radiation. (Solid particles are halted by physical barriers, but upon collision of a certain force, can create radioactive isotopes within the shield material that can then stabilize via release of EM radiation.) All you need to know is *what exact kinds* of rays cause the fogging, and you can design an efficient shield pretty easily. I wish I still had my thermoluminescent detector and a way to read it, though average levels should be easy to find.
    Last edited by 2F/2F; 06-12-2009 at 08:38 AM. Click to view previous post history.
    2F/2F

    "Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."

    - Rob Tyner (1944 - 1991)

  8. #18
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    I have some friends who bought 1000 rolls of infra red film from Kodak's last run (Kodak would not let them buy more). They are off to Europe this summer to use up the film before it fogs.

    Sometimes that is the best storage solution...exposed and developed film does not fog with age.

    Vaughn
    At least with LF landscape, a bad day of photography can still be a good day of exercise.

  9. #19

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    Quote Originally Posted by wiltw View Post
    As for lead, I just found this description in a NASA publication about the methods used to shield a detector from cosmic rays,
    "Passive shielding is used to stop low-energy cosmic rays before they hit the CZT detectors. EXIST uses layered sheets of lead (Pb), tin (Sn) and copper (Cu). This layered approach is called "Graded-Z" shielding, which refers to the order and atomic number (Z) of those metals (Z equals 82 for lead, 50 for tin, and 29 for copper). Materials with larger Z have greater stopping power, and lead is used for the outermost layer. When a low-energy cosmic ray hits the lead it will be absorbed and ionize a lead atom which then emits an X-ray at the "characteristic energy" of lead, 88 keV, in a random direction. Lead does not absorb its own X-rays very well, so to prevent any of those X-rays from getting through the shielding, a layer of tin comes next. After absorbing the 88-keV X-ray, the tin may then emit a 29-keV X-ray. A layer of copper comes last. The few copper X-rays that reach the CZT detector are too low in energy (9 keV) to cause a problem. "

    So simple lead alone is insufficient, as it is necessary to shield from the secondary radiation byproducts that result from the cosmic rays striking the lead, too!
    Any indication on the thickness for each of the layers required ?

    ???
    ---
    I think Kodak did some storage in underground salt mines ....

  10. #20
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    Kodak stored no raw film or paper stock in a salt mine. Among other things, the salt dust would be murder on raw film.

    They did store duplicate business records and formulas in a mine somewhere. Perhaps it was a salt mine, but IDK. It may have been a cave. In any event, this storage of backup data is a routine storage service for large companies.

    PE

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