Shelving

Nancy J. Cyr <ncyr [at] che2__che__umn__edu> writes

>I am writing the specifications for laminated shelving to be used as
>additional shelving in some 25 year old laminated cabinets.  I know
>exterior grade plywood is supposed to be low in formaldehyde and
>should be used instead of particle board, but what about adhesives?

Medite II, manufactured by the Medex Corp., is exterior grade
particle board that utilizes a phenol-formaldehyde adhesive as the
binder. It meets conservation specifications.  The general
specification for plywood or oriented strand board (OSB) is:
exterior grade, American Plywood Association (APA) approved.

Having said that about the spec for phenol-formaldehyde, which is only
the glue and/or binder for the layers or particles, there is still the
issue of the off-gassing of acetic acid and other carbonyl compounds
from the wood fibers themselves that has to be dealt with.  The exposed
surfaces of the shelving boards still need to be coated or covered to
prevent these harmful VOC's from adding to the deterioration of metals,
carbonate-based objects, textiles, paper, and other materials.  The
common misconception with wood-based board materials is that if the
potential formaldehyde problem is solved, then the materials are inert,
which is far from the case.

Pam Hatchfield has done extensive testing and research on this issue and
has found that Camger Water-borne Urethane coating is the best barrier
for museum storage applications.  Keep in mind that no lacquer type
resin coating is a 100% barrier to VOC's or moisture, but this product,
if applied properly in two complete coats according to instructions and
allowed to cure completely, will provide adequate protection.  The other
alternative is to completely cover the exposed surfaces and edges of the
boards with a barrier film such as MarvelSeal.  A film such as Corrosion
Intercept, which is not a barrier film but acts as a passive "sink" for
pollutant molecules, can be used in conjunction with the coated
shelving.

I hope that this has answered the question.  Please contact me off-list
for further details.

Paul S. Storch
Objects Conservator
John and Martha Daniels Objects Conservation Laboratory (JMD-OCL)
B-109.1, Minnesota History Center
345 Kellogg Blvd West
St. Paul, MN  55102-1906
612-297-5774
Fax: 612-297-2967

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                  Conservation DistList Instance 12:2
                   Distributed: Friday, June 12, 1998
                        Message Id: cdl-12-2-001
                                  ***