'Alan Mushing sprays a sample magnetic stripe with a fluid suspension of iron filings – instantly showing up the patterns of zeroes and ones on the card as a series of light and dark bands.' -- That sounds very interesting, i've not heard of anyone doing that before, would you then need an optical microscope to see the patterns I wonder?

Edit: http://www.tetherdcow.com/another-science-experiment/ Has a nice photo of the trick

I just tried some magnetic viewing film I bought a while ago, to see if you can see any lines from a credit card with them, but alas that didn't work.