This doesn't always add gloss to a shell.  It often brings out the color of
a dull shell ... like it looks when it is wet.   It certainly makes the
shell coloration more attractive.      If you look at a display of shells
that have been oiled and one that has not been oiled .... there is a BIG
difference in attractiveness!  I doubt if we are contaminating the shell.
It's a matter of display!

We have shells that are 45 years old with mineral oil on them and they are
just fine!!!  Glycerin especially preserves the perio. On shells that you
would like to save this feature on.

I can't imagine oiling fossil shells.   They are most attractive in dull
white.



From: Conchologists List [mailto:[log in to unmask]] On Behalf Of
Charles F Sturm
Sent: Saturday, September 10, 2005 11:02 AM
To: [log in to unmask]
Subject: Re: Mineral oil?

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

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