Date:         Sun, 1 Jun 2008 07:38:28 -0400
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From:         csturmjr+@PITT.EDU
Subject:      Re: cotton/glue question regarding operculums
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Chris,
I hope that this answers some of your questions.
.................................................
From. Sturm, C. 2006.Chapter 5 Archival and Curatorial Methods. In: The
Mollusks: A Guide to Their Study, Collection, and Preservation. Sturm,
Pearce, and Valdes eds. Universal Publishers, Boca Raton, FL.

5.1 BASIC PRINCIPLES
…The first principle of good curation is to do no harm. Whatever else, do
not treat or handle a specimen in a way that makes it worth less after
curation than it was worth before. One should strive to apply treatments
that can be reversed easily. For example, it is better to use an adhesive
that can be easily removed as opposed to one that will defy the use of a
hammer and chisel to remove it.

The second principle dictates that techniques should be used that cause as
little permanent change to a specimen as possible. It should be assumed
that whatever we do to a specimen will cause some change, and sometimes
the change may not be completely reversible. Thus, we should minimize what
the permanent change to the specimen will be.

The third of the basic principles is to record what techniques you apply
to a specimen, and to record them on the specimen’s label. In this way,
others will be able to tell what was done to a given specimen, whether it
can be undone, and what effect it will have on future analyses that might
be applied to the specimen.

5.2.1 Acid, temperature, and humidity.
…Some woods are more acidic than others and the acidic woods should be
avoided when constructing cabinets. The worst offender is oak. Some of the
better woods are spruce, mahogany, walnut, birch, basswood, poplar, and
balsa. If the woods being used are veneers,
then one has to be concerned with the adhesives used in making the veneers
and whether they will offgas acidic fumes, as well as the type of wood
underneath the veneer. Plywoods are often constructed using urethane
adhesives which can offgas formaldehyde, an acidic compound. If plywood
has to be used, one designed for exterior use is preferred. The adhesives
used are less harmful than those used in interior plywoods, and the
offgasing problem is less intense. Particleboard and pressed wood should
be avoided because of the adhesives used in their production (Hatchfield
1995)….

5.5.2 Vials, jars, and closures. When closing vials there are several
options. Cork should be avoided as an option; it tends to be acidic and
decomposes over time. It also exposes the collection to acidic vapors. A
second option is cotton. This tends to be acceptable if a high quality
grade of cotton is used. Cheaper grades of cotton may be acidic. Before
using cotton, test its pH with a pH-testing pen. The use of polyester
fiber or batting is becoming more common….

5.7 CONSOLIDANTS AND ADHESIVES
…Among the adhesives and consolidants that are considered to be safe and
archival are polyvinyl butyral (Butvar 76 and Butvar 98), polyvinyl
acetate (Vinac), and acrylic copolymer (Lucite, Acryloid B72, and
Paraloid). … Some adhesives and consolidants are no longer
considered archival. These should be avoided. This group includes
polyvinyl alcohol (shrinkage with age), cellulose nitrate (glyptal), and
commercial mixtures. The problem with commercial mixtures (at least those
that do not disclose the ingredients) is that one does not know what
components are in the mixture. Also, without any warning, the manufacturer
can reformulate the mixture. You should also realize that some people
avoid adhesives completely. They do not glue pieces of a specimen back
together unless there is a specific reason to do so. They just put the
pieces in a polyethylene bag and store them that way
.................................................
If you want a copy of the book, several shell dealers carry it, as do
several museums (Carnegie Museum, Bailey Matthews Shell Museum, and you
can read reviews on Amazon.com. Contact me privately if you have any
questions.

Regards,
Charlie
.................................................
Charlie Sturm
Research Associate - Section of Mollusks
Carnegie Museum of Natural History
Pittsburgh, PA, USA

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

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