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    Re: Radium illumination
    From: George Huxtable
    Date: 2010 Sep 6, 00:09 +0100

    All the new evidence Gary provides is perfectly compatible with the advice
    he was given before, which he has summed up well..
    The Radium is still emitting energy, hardly diminished since manufacture.
    It's still emitting alphas, but these are not detected by the radiation
    monitors; a piece of paper is enough to stop them. The monitors are
    detecting more penetrating radiations.
    However, the fluorescent material, which was originally excited by the
    alphas, has lost its ability to fluoresce, though the alphas are still
    stopping in it. The fluorescent material would need to be replaced.
    However, because of the short range of the alphas, it has to be intimately
    mixed in with the Radium. There lies the problem. Overpainting won't do.
    contact George Huxtable, at  george@hux.me.uk
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    ----- Original Message -----
    From: "Gary LaPook" 
    Sent: Sunday, September 05, 2010 11:45 PM
    Subject: [NavList] Radium illumination
    |  I have an A-7 bubble sextant made in 1942. Some A-7s came with
    | electric illumination of the bubble and some were made with radium paint
    | to illuminate the bubble. My bubble has lost its illumination so I only
    | use it for daylight sights. We discussed this issue in the past but I
    | have not been able to find those posts. My recollection of that
    | discussion is that the radium in the original paint should still be
    | putting out radiation but that the paint had lost its ability to
    | fluoresce when excited by the radiation. I asked if I could just put
    | another layer of a florescent paint over the original and whether the
    | new layer would put out light from being exited by the radiation. I
    | believe the response was that the radium put out alpha particles that
    | were not energetic enough to escape the original paint so that this
    | would not work.
    | I got some new information about this on Wednesday. We were coming
    | through customs when horns started blowing and red lights started
    | flashing (I'm being overly dramatic) and two agents said "you'll have to
    | come with us." In the next room I was asked "have you had a stress test
    | recently?" as he held a little black box with colored LEDs next to my
    | hand. "No."  "What's in the box?" "A sextant." Then another guy came
    | with a real Geiger counter and held it next to the A-7. We were stuck
    | for about fifteen minutes while a supervisor went to consult a reference
    | book. Then we were told we could leave.
    | So this pretty much established that the radium was still putting out
    | radiation that was energetic enough to escape the original layer of
    | florescent paint, since it escaped from inside the sextant and the
    | wooden box. It turns out that radium emits alpha and beta particles and
    | also gamma rays. Since the half life is 1601 years the radium has lost
    | less than 3% of its radioactivity since the sextant was manufactured in
    | 1942.
    | So back to my original question, can I use some florescent paint to
    | restore the bubble illumination?
    | gl

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