Well Charles,
I also do not take too much care if shells are chipped or have
growth scars, thatīs natural! But about the shell colors i must
disagree. I think that trying to preserve shell colors is
important, not only for their beauty, but also for identifying
them. Sometimes color can be used as a criteria to easily
separate two close related species (others you can not, of
course...).
As color tend to disappear when shells dry out and we can not
store them in water, i guess oiling them is a good practice.
Some periostracum are very hard to maintain, as those of
Adelomelon ancilla or A. brasiliana, and glicerine or oil are of
great help in those cases...
regards
Fabio Wiggers
--- Charles F Sturm <[log in to unmask]> escreveu:
> Matt and Conch-l'ers,
>
> I agree with the general techniques that folks have been
> writing about
> regarding using mineral oil or silicon oil for adding gloss
> back to a dull
> shell. I agree with avoiding animal and vegetable based oils
> as they
> become rancid over time. However, I would like to ask the
> question
> differently, "Why oil shells?" Why do we need to have every
> shell appear
> glossy? I would argue that in doing this we are losing
> information and
> possibly contaminating specimens.
>
> I collect fossil mollusks for the most part and I never add a
> surface
> protectant to them. I will soak some of them in a consolidant
> (Butvar 76
> in acetone) if they are very friable. I note such treatment on
> the labels
> accompanying these specimens.
>
> I rarely collect live material; most of my self-collected
> Recent shells
> are freshly dead or specimens that have been banging around
> for a while in
> the surf. To me the dullness of the shells is an indicator of
> postmortem
> changes. This is information that I do not want to lose. Also,
> if someone
> would ever want to use one of these specimens for destructive
> testing
> (i.e. chemical analysis) a treatment with oil might very well
> make such an
> analysis meaningless. At the Carnegie Museum, we occasionally
> receive a
> request for a specimen that may be 50-100 years old so that
> such analyses
> can be done and compared to the chemical composition of Recent
> shells.
>
> Some will say that you have to prep the shells to preserve the
> periostracum (for instance in Unionoida). This can also be
> accomplished by
> carefully controlling the temperature and relative humidity of
> the space
> where one stores a collection.
>
> So in the end I pose the question, "Can we only appreciate
> shells if they
> are glossy, or can we save time and leave them as they came
> from their
> environment?" One possible alternative that may satisfy both
> camps is to
> treat some (maybe for a display) and store a few others
> (untreated) for
> posterity in a zip-lock bag.
>
> While this question is rhetorical and posed to have us think
> about
> alternatives to how we do things, I would also be interested
> in reading
> others thoughts on this subject.
>
> Regards,
> Charlie
>
******************************************************************************
> Charlie Sturm, Jr
> Research Associate - Section of Mollusks
> Carnegie Museum of Natural History
> Pittsburgh, PA, USA
>
> Assistant Professor - Family Medicine
>
> [log in to unmask]
>
>
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