Why should magnete are kept from magnetic media
Answers
The term 'magnetic media' is used to describe any record format where analogue or digital information is recorded to and retrieved from a coated matrix that can be magnetised.
Common types of magnetic media are:
audio reel-to-reel and cassettes tapes
video and computer tapes on open reels or in cassettes
hard disk drives, (HDD)
floppy disks or diskettes.
Magnetic tape has a plastic carrier coated with a matrix of metal or metal oxide particles, a resin binder and other ingredients such as lubricants and fungicides. Sometimes the tape has an antistatic coating on the back to reduce static charge build-up and to improve its winding capability.
Magnetic hard disks usually have an aluminium base, coated on both sides with a metal or metal oxide matrix. They have wide application in computing as the principle storage medium. Floppy disks and diskettes consist of a plastic base with a magnetic matrix on one or both sides. They are enclosed in a rigid, plastic protective jacket. Although an obsolete medium they are still likely to be found in collections and are a priority for transfer to new media.
Preservation and storage
All materials degrade at different rates over time. We cannot prevent this inevitable deterioration, but we can slow it down. Below are examples of the types of deterioration to which magnetic media are prone.
Older acetate audio tapes can become brittle and easily broken. The magnetic coating on tapes and disks can deteriorate and subsequently flake off the base.
Print-through, which is the transfer of a signal from one loop of tape onto an adjacent loop. This takes the form of a pre-echo and can be obviated by storing audio tapes 'tail-out' on their reels.
High temperature and humidity and fluctuations may cause the magnetic and base layers in a reel of tape to separate, or cause adjacent loops to block together. High temperatures may also weaken the magnetic signal, and ultimately de-magnetise the magnetic layer.
Tapes are particularly susceptible to mould because pockets of air trapped in the windings can create microclimates which will support mould growth.
Dust, dirt, grease and chemical pollutants can promote moisture condensation and oxidative deterioration. These contaminants also interfere with the contact between the playback head and the tape, causing audio signal drop-outs.
Magnets or magnetic fields can cause information loss on a tape or disk if it is in close proximity for long enough because information is encoded on magnetic media by the alignment of magnetic particles. The degree of risk depends on a number of factors; proximity of the media to the source of the field; strength of the field, and duration of exposure. Running a vacuum cleaner past the shelves will probably not cause any damage, because magnetic effects decrease with distance.
Always handle magnetic media as carefully as possible.
Pick up magnetic tapes by their protective cases – do not touch the tape or disk surface.
Wear lint-free gloves or ensure that hands are clean and dry.
Suive case, rather than directly onto the magnetic tape or disk.
Only remove items from their protective packaging for immediate use, and return them to their containers directly after use.
Audio cassettes and open reel tapes should be wound to the end of one side after use and not left in a partly wound state for any length of time. Avoid use of the 'pause' mode with audio and video cassettes.
When moving magnetic media ensure that it is properly packed in custom-made transportation canisters and is not bumped or dropped. Consult specialist freight and courier companies when transporting large quantities of magnetic media.
Magnetic media is sometimes supplied in cardboard enclosures. These can be used for the storage when in good condition. However, when they are older or damaged, they tend to generate dust.
Tapes should be stored in cases made of non-magnetisable material, preferably an inert plastic such as polypropylene. Cases should have internal lugs to securely hold the tapes by the hub. They should be strong enough to protect the cassettes from external damage and close tightly to keep out dust.
Reels or cores used for winding tapes should be clean and undamaged. Reels should be made of aluminium or a stable inert plastic.
Floppy disks and diskettes should be stored in protective envelopes that have a non-abrasive surface and are resistant to the build-up of static electricity. Tyvek envelopes are widely available and are suitable for this purpose.