Why was glass or plastic used to separate the filings from the magnets in the experiments?
the experiment required me to place a bar magnet on a table, then place a sheet of glass or plastic over the magnet before sprinkling the filings over it. i had to do this for both a bar magnet and a horseshoe magnet.

The glass or plastics are non-magnetic materials, which means that they wouldn't be affected by the permanent magnet that you will use. They act as a virtual spacer between the magnet and the sprinklings. The sprinklings will orient themselves following the shape of the magnetic field created by from the magnet.