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    Re: Sextant on ebay
    From: hellos
    Date: 2006 Sep 6, 13:26 -0500

    Herbert-
    Not that a bare metal surface would necessarily get hotter than a black one,
    but bare metal seems to burn flesh better than painted metal, simply because the
    paint insulates to some degree from the thermal mass of the metal. Maybe that's
    a myth, maybe it various with the nice thick coatings that are used as opposed
    to "radiator paint" blacking.<G>

    Let's experiment, and put some heavy aluminum castings under heatlamps, one
    bare the other coated with thick black paint, and see which one burns flesh
    faster. Not for the depth of burn, but for the worst "ouch factor" on first
    contact. (What, no volunteers? Even in the name of science?! <G>)

    This is only what I suspect. I'm told that radiators (as in cars) work better
    with a thin coat of flat (radiative) black paint but worse with a heavy coat of
    any paint, compared to bare metal. Supposedly because of the actual structure of
    the paint layer, not just the color. And in theory the Bedou should be wearing
    white robes not black...but black actually works better once you go deeper than
    just reflecting hear. Or so says that other theory.<G>







    ----- Original Message -----
    From: "Herbert Prinz" <ml@hprinz.us>
    To: <NavList@fer3.com>
    Sent: Wednesday, September 06, 2006 12:31 AM
    Subject: [NavList 1170] Re: Sextant on ebay


    >
    > Red wrote:
    >
    > >  "it is not often that you see a polished metal sextant. " Probably
    > > because it is greatly impractical. In the noon sunlight, it would burn
    > > your hands (bare metal) and blind you from glare spots.
    >
    >
    > Why would a highly reflectent polished surface get hotter than one that
    > is painted black? In fact, Plath tried to find a compromise between
    > reducing heat absorption and avoiding glare spots with a model that was
    > painted white.
    >
    > Herbert Prinz
    >
    > >
    >
    >
    > --
    > No virus found in this incoming message.
    > Checked by AVG Free Edition.
    > Version: 7.1.405 / Virus Database: 268.11.7/437 - Release Date: 9/4/2006
    >
    >


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