Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,011   Posts: 1,524,678   Online: 736
      
Page 2 of 2 FirstFirst 12
Results 11 to 18 of 18
  1. #11
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,942
    Images
    65
    Ray;

    A charged object, when moving, generates a magnetic field regardless of charge (+ or -). Therefore either type of charge can affect an electronic balance.

    PE

  2. #12

    Join Date
    Aug 2005
    Location
    Earth
    Shooter
    Multi Format
    Posts
    1,560

    Puttting some light on the thing...

    Quote Originally Posted by wildbillbugman View Post
    Hi All,
    I am realy reluctant to post this question. It seams silly. But here it is: Do magnetic fields impact emulsion formation. I always use a magnetic stirring barr.I wonder if I would get different results with an overhead mixer.
    Sorry about this,
    Bill

    It is interesting to keep in mind that some Electromagnetic Waves which have a magnetic field component will not only affect but will actually EXPOSE an emulsion!

    I know you had something else in mind when you wrote your question.
    but there is still much that is mysterious to many people about common ordinary phenonoma.

    Recent discussions in England about the nature and possible roll of magnetic fields in some photographic phenonmena come to mind.

    I do not think your question is silly.
    Some people have felt that the direction of stirring a significant item to be controlled.

    Now that sounds silly, yet they were respected scientists/emulsion researchers whose work was incorporated in many commercial emulsion formulas.

    Ray

  3. #13
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,942
    Images
    65
    I have heard the same Ray, but only with respect to the direction of flow of the emulsion down a drain or through a pump. It can be important, but only in very rare cases where turbulence causes bubbles or nonuniform mixing.

    In other words, the problem with mixing stems from other than magnetic, and other physical considerations enter into this sort of problem.

    As for electromagnetic exposure of emulsions, you are generally confined to radiation of some sort, not pure magnetic phenomena. If magnetic fields exposed film in any way, we would have a lot of foggy MRIs.

    PE

  4. #14

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    Quote Originally Posted by Ray Rogers View Post
    In any case, I submit the opinion that what is or is not mysterious is in the eye of the beholder and even in the face of appearent scientific understanding, there are somethings that for some people remain amazing and mysterious.
    While I hope I don't violate Clarke's First Law here, I'd like to invoke his Third Law:
    "Any sufficiently advanced technology is indistinguishable from magic."

    Quote Originally Posted by Ray Rogers View Post
    It seems there is always something held out of our view, off stage so to speak and that is where the mystery resides, in the unconscious and in that twilight between the conscious and the unconscious.
    Or in the case of diamagnetism, it resides in the field that the electrons make as they smear themselves through space as they zip about the nucleus.

  5. #15

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    Quote Originally Posted by Ray Rogers View Post
    Well, I am just curious, I understand that silicone materials tend to collect electrons and become negatively charged... if this was the case what would you expect the scale to do? Increase or decrease?
    Well, I can't say the balance will go high or low. I think it all depends on the balance. I just know they wander about and you sit there waiting for a reading to become stable. You're right about the negative charge, but I think as the balance moves about, some internal parts (pans, arms, housing...) will attract or repel each other, and the charge may disappate through the balance, and mess the stability up more. It just keeps changing and you have to sit there and wait...

    When weighing things that are even just slightly warmer than the scale/balance which is trying to wiegh them will usually cause the reading to be high, as a convection current from the warm air rising from the object will pull the balance pan upwards with the movement of the air. That's another bane to people that wiegh a lot of things...

  6. #16

    Join Date
    Jun 2004
    Location
    Portland, OR
    Shooter
    4x5 Format
    Posts
    3,268
    Quote Originally Posted by Ray Rogers View Post
    How do those people you mention that do a lot of weighing of really dry objects at less than 0.001 g precision, handle the problem?

    Is the earlier or later indicated weight to be taken as the most "accurate"?
    Ray - the first thing you can do, is sit and wait...

    Another thing that I've seen people try is to put those little StaticMaster strips, like on the photo brushes, in the enclosure of the balance. They have polonium-210 in them and they emit alpha particles - positively charged helium nuclei. They postive alpha particles neutralize the negatively charged electrons. I've never really found them to be effective when used with balances, but some people believe they help...

    One thing I do is open the door of the balance, and blow in a gentle breath to add some humidity to the air. It doesn't always seem to help, but it seems like it does sometimes...

    Another thing to remember, is to try not to induce any static charge on whatever it is you are going to weigh. I once worked with a guy, who before wieghing out chemicals, would shake the bottle to mix the contents. He would then put in his metal spatula and put it in the container, load up a bit of material, and then pull it out. Works fine, on most things. Well, one day, he had some chemical that was really dry, and it would make a charge on it every time he shook the bottle. As he pulled the spatula out the neck of the plastic bottle, the powder would come flying off the spatula and fly all over the benchtop! It was rather funny to watch. He was totally confused as to why it was happening. I suggested that he not shake the bottle, and next time he weighed that chemical out, he didn't have the stuff come flying out. So try not to induce any static into whatever it is you are wieghing.

    Oh, and when it's the middle of the winter, and the air is cold and dry, you will probalby have more problems than when it's warm and wet outside.

    Finally - always go with the last weight on stuff. You can't trust a reading because it's moving, just wait until it stops, or at least the variance gets low enough that you don't need a more accurate reading.
    Last edited by Kirk Keyes; 10-25-2008 at 05:33 PM. Click to view previous post history.

  7. #17
    Joe VanCleave's Avatar
    Join Date
    Jan 2004
    Location
    Albuquerque, New Mexico, USA
    Shooter
    Pinhole
    Posts
    482
    A bit off-thread, but:

    This thread reminded me of a bit of news that was reported last week. Some researchers unearthed an old paper from a (IIRC) Soviet scientist who conjectured that unrolling adhesive tape in vacuum would release X-rays; this conjecture was recently confirmed; the breaking bonds of the tape's adhesive, in vacuum, would build up enough voltage potential to break electron bonds and release X-rays. Sufficient X-rays to fog a dentist's X-ray film, for instance. A whole new field of study has now apparently been started, as on the video I watched they were able to achieve a 10x increase in X-ray flux by merely using a different brand of tape. This promises an entirely new technology for generating X-rays without HV power supplies and such gear. Of course, most new discoveries end up as weapons, so this will be interesting to watch.

    Anyway, back on thread ... I have a StaticMaster dusting brush, but it's been maybe 15 years since it was new, so using it is more like a ritual of faith than real science, since the Polonium has long since decayed. Still, it's a nice conversation starter with friends who know next to nothing about photography; it's not just toxic chemicals, but radioactivity, too!

    ~Joe

  8. #18
    Photo Engineer's Avatar
    Join Date
    Apr 2005
    Location
    Rochester, NY
    Shooter
    Multi Format
    Posts
    22,942
    Images
    65
    Joe;

    Peeling off tapes releases electric discharges. You can see this when you rip off the end tapes on 35mm or 120 film. It does fog film. Static discharge contains high levels of UV and there may be some X-ray depending on the power of the discharge, but the atmosphere is very opaque to X-ray and so below a certain level, it cannot be seen. In fact, all X-ray sattelites must be in orbit as stellar X-ray emission cannot penetrate to the surface of the earth.

    So, peeling tape in a vacuum and releasing X-ray seems logical to me. It may have gone unobserved due to the weak nature of the release and absorption by air. In fact, the UV release may be a visual component. I seem to have read somewhere that they detected weak X-ray emission from lightning bolts as well. IDK for sure, been years ago.

    PE

Page 2 of 2 FirstFirst 12


 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



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