Magnetic media.

Magnetic media have become an integral part of our everyday society. We consider following formats as magnetic media

• Audiotape
• Videotape
• Computertape
• Computer floppydisc
• Hard disc

The process of making magnetic records is based on magnetic processes that occur in an emulsion layer. For a better understanding of the processes, the components of magnetic media should be known.

Magnetic media as we know them are mainly composed of 2 or 3 components. The basic components are:

• A basematerial that acts as a support and which can be rigid or flexible.
  • Rigid supports are mostly of aluminium or glass and used in hard discs.
  • Flexible materials include polyvinylchloride (now abandoned), cellulose-acetate and polyester. They are used for audio- and videotape, computertape and floppy discs.
    
    
• A binding layer which is nowadays mostly made from polyurethane. To be able to record the information use is made of magnetic elements which are embedded in the binding layer. Different kinds are ferric oxides and chromium dioxide.
  
  
• A third layer is more frequently used on the back nowadays as a protection against mechanical damage through the apparatus.

The preservation of photographic materials is being influenced by the stability of the support and the emulsion layer. This stability is being affected by temperature, humidity, light, UV-radiation, chemical pollutants, magnetic fields, demagnetization, damaged apparatus and even ordinary use. The most important deterioration occurs because of hydrolysis, in which the binding layer forms acids when interacting with moisture in the air.