Thin plastic or metal is used as the base material for magnetic tape. Most magnetic tapes are made with plastic because of its flexibility, resistance to moisture problems like mildew and stability through temperature and humidity changes.
The base material is coated with particles that are able to be magnetized. Iron oxide, chromium dioxide, metal particulate and barium ferrite are the most common particles used with magnetic tape.
An organic resin is used to bind the oxide particles to the base material. The glue must be flexible to avoid peeling and cracking, yet strong enough to keep the oxide particles on the base material.