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RI of tempered glass

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  • Wyatt, Mat
    I have a strange piece of tempered glass. There is a wide range of RI on it. I can t get the GRIM2 to nail down a reliable RI value. The best I got was when
    Message 1 of 2 , Apr 1 7:25 AM
      I have a strange piece of tempered glass. There is a wide range of RI on
      it. I can't get the GRIM2 to nail down a reliable RI value. The best I got
      was when I broke a small "pebble" of broken glass and tried very carfully to
      remove glass from the middle. Does anyone have a good technique for
      analyzing the RI of tempered glass? In the past I haven't had any trouble
      matching up the RI, but in this one, there seems to be a large variance in
      RI from the center of the glass to the edges.

      Any suggestions would be greatly appreciated.

      Thanks,

      Mat
      Cincinnati

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    • spartantroy
      Using a GRIM3, I ve experienced that some glass has a tighter RI range than others. While it can be frustrating to have such a wide range, if your Q and K
      Message 2 of 2 , Apr 4 6:22 AM
        Using a GRIM3, I've experienced that some glass has a tighter RI
        range than others. While it can be frustrating to have such a wide
        range, if your Q and K both exhibit this range, it can actually be a
        good comparison. If you're able to show that the variance is
        similar from surface to middle for both Q and K, even better! On
        the flip side, if your K has a wide RI range, and your Q sample is a
        single small fragment that is somewhere in the wider K range, you're
        left with the "could have originated from a common source" that
        doesn't end up meaning a whole lot (and you should describe that to
        the investigator). That's what sometimes happens with real-world
        samples - the science isn't bad, but the significance may not be
        very strong. It is likely that the GRIM is obtaining accurate and
        precise readings (provided your calibration curve and controls all
        check out fine), but your glass simply has quite a variability to
        it. All you can do is work with what you've got and not say more
        than the results allow. Out of curiosity, what kind of range are
        you getting? Contact me off-list if you wish.
        Troy Ernst

        --- In forensic-science@yahoogroups.com, "Wyatt, Mat"
        <mat.wyatt@h...> wrote:
        > I have a strange piece of tempered glass. There is a wide range
        of RI on
        > it. I can't get the GRIM2 to nail down a reliable RI value. The
        best I got
        > was when I broke a small "pebble" of broken glass and tried very
        carfully to
        > remove glass from the middle. Does anyone have a good technique
        for
        > analyzing the RI of tempered glass? In the past I haven't had any
        trouble
        > matching up the RI, but in this one, there seems to be a large
        variance in
        > RI from the center of the glass to the edges.
        >
        > Any suggestions would be greatly appreciated.
        >
        > Thanks,
        >
        > Mat
        > Cincinnati
        >
        > This e-mail message, including any attachments, is for the sole
        use of
        > the intended recipient(s) and may contain private, confidential
        and/or
        > privileged information. Any unauthorized review, use, disclosure
        or
        > distribution is prohibited. If you are not the intended recipient,
        > employee or agent responsible for delivering this message, please
        > contact the sender by reply e-mail and destroy all copies of the
        > original e-mail message.
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