Re: How do magnets effect cassette tapes and how do you protect them?

Magnetic fields will erase or scramble the information on cassette tapes if the 
fields are strong enough. Refrigerator magnets are plenty strong enough. You can 
shield things from electrical fields by wrapping them in a conductor. Unlike the 
case of electrical fields, there really is no simple shielding for magnetic 
fields (except of course superconductors). Cassette tapes are really a thin 
layer of magnets. The magnetized (recorded) tape can "print through" from one 
layer to another over time. You can minimize this phenomenon, by fast forwarding 
and rewinding stored tapes every year or so.

You protect tapes by keeping magnets away from them. Educate people about this 
danger; don't carry magnets around with tapes or computer disks.

Hope this helps.

David Winsemius.