Engraving

The following discussion took place in sci.chem and is reposted here
without the knowledge or consent of the authors.

    Article: 4841 of sci.chem
    From: tspcjr [at] lure__latrobe__edu__au
    Subject: Chemical process to reveal engraving (wanted).
    Date: 18 Oct 91
    Organization: VAX Cluster, Computer Centre, La Trobe University

    G'day,

    This is one of those "Posts for a friend" jobs.

    A friend has an interesting metal object that they picked up in an
    antique sort of store that was obviously once engraved, but has just
    as obviously been filed away.  They'd love to know if there is any
    chemical process that will allow the old engraving to be seen (if
    only for a short length of time).

    Any nice recipes out there?!

    Thanks,

    Chris.


    Article: 4856 of sci.chem
    From: v087n562 [at] ubvmsb__cc__buffalo__edu (Lewis A Bernstein)
    Subject: Seeing what was engraved
    Date: 21 Oct 91
    Organization: University at Buffalo

    One way to see what was engraved on an object is relatively easy.
    All one needs to do is to mildly etch (dissolve) the object that you
    wish to see the engraving on.  The reason that this will work is
    when an object is engraved, or stamped or deformed in some other
    way, the stresses  in the material go beneath the first few layers
    of atoms and they are also deformed.  Because of these deformations,
    when the object is etched, it will etch at different rates due to
    these inherent stresses.  If you file away the face of a penny and
    then put it into a dilute solution of nitric acid (nitric acid
    dissolves Cu readily) you should be able to see lincoln's head again
    along with the date, etc.  Hopefully that will help.

    Lewis A. Bernstein
    Dept. of Chemical Engineering
    SUNY-Buffalo

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                  Conservation DistList Instance 5:25
                 Distributed: Sunday, October 27, 1991
                        Message Id: cdl-5-25-009
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