National Archives of the Netherlands (Ministry of Education, Culture and Science)

Magnetic media

Magnetic storage media are comprised of layers bound together with chemicals.

A synthetic base (originally chemically unstable cellulose acetate, but the more stable polyester has been used since the 1960’s), is covered with an emulsion of magnetised material, such as iron oxide, chrome dioxide, or a metallic pigment.

A polymer adhesive (binder) fastens the emulsion onto the base. A plastic substrate or backing material can be applied to the base to prevent friction, achieve better performance, and prevent curling or separation of the electrostatic layer.