Medium density fiberboard

Our regional distributor of Sierra Pine's Medex brand Medium Density
Fiberboard is no longer stocking this product, or any of its
formaldehyde- free siblings (medite, medite II).  They have instead
decided to stock a product called "Extira", manufactured by
CraftMaster Manufacturing, Inc. <URL:http://www.extira.com>. Extira
is an exterior grade product, also formaldehyde-free, but it has
been suffused with zinc borate to deter insect pests.  While their
literature promotes its good qualities (better screw holding,
smoother face, more consistent density throughout) it doesn't
mention much about zinc borate.

My questions: is zinc borate a harmful product to put into museum
case work? Does it off gas any potentially harmful substances which
might endanger objects within?  If properly sealed with shellac or
paint will the problem be solved?  If it is bad, does anyone know of
a Medex distributor near Cleveland, Ohio?

Jim Williams
Project Coordinator
Intermuseum Conservation Association
2915 Detroit Ave
Cleveland OH 44113
216-658-8700


                                  ***
                  Conservation DistList Instance 17:49
                  Distributed: Friday, January 9, 2004
                       Message Id: cdl-17-49-018
                                  ***