In addition to what has already been opined, I will direct folks to the
following paper which I just came across in my files...

The effects of relative humidity on mollusc periostracum and the use of
coatings to prevent loss. Joanna Morton. Collection Forum 20(1-2): 67-82
(2006).

This journal is published by the Society for the Preservation of Natural
History Collection. A link to the paper is

http://www.spnhc.org/media/assets/cofo_2006_V20N172.pdf

scroll down to page 78 of the PDF.


> Thanks Charles,
>  Should have looked at my copy first. Your book answers most questions
> fully.
>  Thanks,
>     Carole
>
>
> In a message dated 12/13/2014 9:09:03 P.M. Eastern Standard Time,
> [log in to unmask] writes:
>
> Carole,
>
> I have have kept a number of thin walled Viviparidae  and Pyganodon in
> ziplock bags without any other treatment. They have held  up well for the
> past 10 years. A few which I did not put in ziplocks (an  oversight)
> cracked within a few months.
>
> The ziplock bag, while  permeable to moisture, isolates the specimen from
> rapid changes in relative  humidity and seem to protect specimens
> reasonable well without  "contaminating them with various chemical.
>
> On the other hand, if the  specimen is going to be part of a display or
> one
> that will be handled by  people, then some of the preservation techniques
> mentioned would be worth a  try.
>
> I also offer the following which appeared in Chapter 2 of The  Mollusks:
> Aguide to their collection, study, and preservation
>
> Animal  and vegetable-based oils will become rancid with time and should
> be
> avoided. Silicon oil is a relatively inert substance. Its stability,  lack
> of odor, and safety profile have made it a substance that people  are
> comfortable using. The silicon oil is cut with naphtha or mineral  spirits
> 1 part to 2-4 parts. Shells are dipped into this mixture and then  placed
> on a flat surface. The solvent evaporates leaving behind a thin  coating
> of
> silicon. If diluted appropriately the amount of silicon oil  remaining
> should not leave the shell feeling greasy or tacky. Too much oil  makes
> the
> shell slippery and a “dust
> magnet”. Mineral oils can be used  in a similar fashion.
>
> A number of collectors have used a solvent called  WD-40® to brighten the
> surface of a shell or to preserve the periostracum.  WD-40 is a petroleum
> distillate. Some collectors dilute it 1 part to 3-4  parts naphtha or
> mineral spirits and then dip their
> shells into this  solution. Others use the WD-40 full strength. We do not
> recommend WD-40 for  one preservational aspect - it is a proprietary and
> secret formula. Such  mixtures are of unknown composition and can be
> changed at any time. Thus,  you are
> never certain what you are putting on your shells. If you are going  to
> apply a coating to your shells, you do not want to apply it full
> strength.
> This full strength coating will often make the shell tacky and  slippery.
> Many collectors dilute the oily substance with naphtha or mineral
> spirits.
> Diluting the oil one part to three or four parts of solvent is  often
> sufficient. When the solvent evaporates, it leaves behind a thin  coating
> of the oil. Also, the thinned oil is able to penetrate into the  shell
> deeper than the full strength oil would. When using solvent, make  sure
> there is adequate ventilation and no sources of open flames. While
> naphtha
> and mineral spirits are relatively low toxicity, they can act  as
> respiratory irritants. They are also flammable, thus no sources
> of  flames or sparking should be present.
>
> Clench (1931) described a process  of mixing paraffin with xylene. Place
> 120 g (4 ounces) of paraffin in 300  ml (10 ounces) of xylene. Warm this
> in
> a water bath to dissolve the  paraffin in the xylene. Shells are dipped
> into the solution and then  placed
> on a flat surface to dry. The xylene will evaporate leaving behind a  thin
> coating of paraffin. Remember that xylene is flammable so avoid  open
> flames. Xylene is also a respiratory irritant, so this method should  only
> be performed in a fume hood or a well ventilated area such as  outdoors.
>
> You should also keep in mind that many collectors and most  museum workers
> apply no surface coating to shells. Generally, if you keep  the
> temperature
> and humidity level of your storage area within a range of  16-21ºC
> (60-70ºF) and 50-55% relative
> humidity, there should be no  concern with the periostracum peeling (See
> Chapter 5, Archival and  Curatorial Methods). Also, there is nothing wrong
> with a slightly faded,  pristine shell as opposed to one that is shiny but
> chemically  adulterated.
>
> Clench, W. J. 1931. A preventive for the scaling of the  periostracum.
> Nautilus 45:  30-31.
>
>
> Regards,
> Charlie
> .................................................
> Charlie  Sturm
>
> Treasurer
> American Malacological Society
>
> Research  Associate - Section of Mollusks
> Carnegie Museum of Natural  History
> Pittsburgh, PA, USA
>
> Associate Professor - Family  Medicine
> Fellow-American Academy of Family Practice
> Fellow-Academy of  Wilderness  Medicine
>
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Regards,
Charlie
.................................................
Charlie Sturm

Treasurer
American Malacological Society

Research Associate - Section of Mollusks
Carnegie Museum of Natural History
Pittsburgh, PA, USA

Associate Professor - Family Medicine
Fellow-American Academy of Family Practice
Fellow-Academy of Wilderness Medicine

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