Magnetic closures

Richard Minsky <consdist [at] bookarts__net> writes

>Is there any documentation of longevity tests on these materials,
>with a comparison of different brands?  Is there a parameter in
>standard nomenclature that addresses the durability of magnets? Does
>it make a difference to longevity whether it is magnet to magnet or
>magnet to metal? My concern is that in 500 years or less the
>closures will not work. This information is needed both for archival
>containers for existing works and in the design of new works.

Last year William Minter showed me a selection of Rare Earth Magnets
which he wished to use for closures (these and other types of
magnets are available for the American supplier McMaster Carr). They
were pressure formed Samarium-Cobalt or neodymium-iron-boron magnets
of very high magnetic strength for their small size and weight,
Nickel plated they can be as thin as 0.06 inches giving them much
greater potential than the thicker weaker rubber bonded flexible
magnets. They could easily be doubled up (or more) to give the
required magnetic grip without becoming bulky. The technical data
given by the supplier lists them as having very high resistance to
demagnetization and high corrosion resistance, but against what
parameters they do not give, perhaps the producers may have more
information.

Ultimately I think a box or enclosure that is simply well made and
remains snugly closed without the aid of an additional closure is
much better. When a closure is needed magnets have a certain
attraction. Traditional closures and ties are notoriously prone to
damage, ties and clasps eventually tear or break, velcro weakens and
the self adhesive velcro quickly drops off. The closures add bulk,
can catch on shelves or other objects and rely on the intelligence
of the user to properly reconnect. Magnets if incorporated well
within the structure could be very user friendly and have long
usage.

I suppose the other issue is the working lifetime of a protective
enclosure. I would be satisfied, I think, if a hand made clam shell
box lasted a couple of hundred years with the present level of
archival materials (boards, glues, etc) and collection access. 500
years is a long time and I would hope (perhaps naively) that my
successors will replace the enclosures within this period when they
have reached the end of their useful working life.

Neill McManus
Book Conservation
Jewish National and University Library
Jerusalem


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                  Conservation DistList Instance 18:27
                Distributed: Thursday, December 16, 2004
                       Message Id: cdl-18-27-005
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