RE: [AV Media Matters] cassette tape shelf life?

[kbradley@nla.gov.au]

	>This has been a concern of mine- vacuum cleaners in vaults. So far
we sweep
	>ours, and I've planned a canister-type with the hose inside and the
>canister exterior to the vault. Anyone thinking about this AC motor issue?>

AC motors have very uneven fields, and at a distance of a few cm (substitute
a bit under 0.4 inches if you're from US!!), it can quite easily reach the
sort of field strength that might cause some degredation of the signal (not,
I stress, anywhere near erasure).  This is probably a problem only with
analogue fe2o3 type material as the coercivity is quite low compared to
other formulations.  As our cleaners wear their vacuum cleaners on their
back, and bang up and down between the rows, we banned them from the vault.
So now our cleaners used a dampened mop (no water is allowed in the vault
either) and wipe up the dust.  Static cloths are used to wipe shelves.  We
have a decent filter on our airconditioning.  We also have only hand wound
compactus, as strapping elctromagnets to metal shelves went against our base
instincts (and tapes are a light load compared to paper).

The main reason to keep out vacuum cleaners, however, is as our erstwhile
moderator has said, they spew out as much fine particulate material as they
pick up.

Kevin Bradley
Manager: Digital and Audio Preservation Resources
National Library of Australia
Canberra   ACT 2600
AUSTRALIA

Tel:  +61-2 6262-1381
Fax: + 61-2 6262-1653
Email: kbradley@nla.gov.au
NLA home page: http://www.nla.gov.au
Change is inevitable, except from a vending machine