Dear Charles;
        Certainly oil will protect and preserve periostracum.  I think, as you
suggest, that it also prevents shells from losing moisture, which is
harmful to the surface of the shell, and results in loss of color and
gloss.  The practice is quite acceptable to most collectors, since it
does enhance colors, but is easily removed if that is what the collector
decides to do.
        Re lip filing, it is really not acceptable to most collectors - i hate
getting shells with filed lips, since they just sit around on the lists
forever, unless one puts a very low price on them.
        It is usually fairly easy to tell if a shell has been polished: it will
be shinier than normal, and smoother. A close look under 10X, with a
handlens, will confirm: the little irregularities and tiny scratches
that occur on even "GEM" cowries and olives will be gone: it is quite
easy to figure out which shells one should return due to tampering!

From the still-white-but-melting-fast (got up to nearly 40 F today!) North;
-Ross.

Charles Geerts wrote:
>
> Dear Ross,
>
> Thank you very much for your circumstanciated reply.As far as the practice
> of oiling shells is concerned, I can accept it if it preserves the
> periostracum that might have a tendency to peel off after some time in
> rather dry conditions.I can also understand conchologists who like to use
> make up ( oil)to enhance the colors. But is there scientific evidence that
> the oil otherwise " preserves" as you state it. If so, I would like to hear
> about that evidence from you or anyone who might have it.I suppose any
> shell has a quantity of H2O in it. Does oil prevent the water to evaporate?
> Should we prevent water to evaporate? Does oil prevent colours to fade away?
>
> I further reviewed some posts and read with lots of interest one dedicated
> to lip filing in conus and other shells.
>
> My question at this stage of the discussion is: is there any means of
> finding out by  simple observation whether a shell with a natural gloss
> (cypraea, oliva, marginella and even some conus) has been enhanced by means
> of polishing powders?
> Best regards
> Charles

--
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