Magnetic, optical and audio-visual media can be used for storing digital records, and physical records that have been digitised.
However, magnetic, optical and audio-visual media may be susceptible to damage. This depends on the type, format, quality of manufacture, handling and treatment, and proper storage conditions.
You should implement controls to protect the media from damage during handling and usage.
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Magnetic media has particles that retain the coded information in a magnetic layer. These particles can become unstable, leading to a gradual loss of signal quality and eventually to total information loss.
Flexible magnetic disks are prone to catastrophic loss of data due to physical degradation and exposure to magnetic fields.
Magnetic tapes in humid environments are also particularly susceptible to mould.
The critical portion of an optical disc is the data layer, which can be damaged relatively easily. Small amounts of degradation can cause significant information loss.
Optical media are susceptible to:
- solvents–they can affect the lacquer layer and subsequently the metal layer on a CD
- markings or deposits (e.g. scratches, fingerprints) on the data side
- age related damage–the polycarbonate plastic layer tends to slowly lose shape, making them difficult to read
- mould, moisture and dust
- high or dramatic and sudden changes in temperature and humidity, including direct sunlight
- corrosion of the metal layer–certain metals, such as gold, are more resistant to corrosion than others
- inks, adhesives from labels and damage from writing implements–even on the ‘label’ side, they can easily damage or corrode the plastic or lacquer layer, and subsequently the metal layer.
Storage for magnetic and optical media must have controls in place to reduce the risks.
- Temperature and humidity should be as constant as possible.
- Avoid power variations or power spikes.
- Avoid paper and cardboard enclosures, and remove paper (e.g. information booklets) from cases as they generate dust and increase moisture.
- Media should be stored upright. Media should not be stacked, stored horizontally or packaged so that they lean against each other.
- Hard disks which are not part of networked storage should be stored in anti-static bags.
- Earth metal storage shelves.
- Magnetic disks should remain powered as intelligent storage arrays can test for data corruption and self-repair (within limits). If disks must be powered down for extended periods, they should be ‘parked’ according to manufacturer instructions.
- Media should be stored in reasonably dust-proof cases made of an inert plastic, such as polypropylene, or non-magnetic material. Polyvinylchloride (PVC) is unsuitable because it contains substances that may be damage the media.
- Tape cases should have fittings to hold the tapes in position by the hub–they should be strong enough to protect the cassettes from physical damage and they should close tightly to keep out dust particles.
- If optical discs must be labelled, use a water-based felt-tip permanent marker to mark the label side of the disc. Do not use ballpoint pens, pencils or adhesive labels.
Microfilm should be stored in specialist containers and in specific environmental conditions.
Microfilm spools must be wound on with the emulsion side facing outwards.
They should also:
- be plain black plastic
- be free of poly vinyl chloride (PVC) and peroxide
- have no film stopper lugs.
Film must not be secured around the spool with rubber bands, string, tape, paper, sticky tape or any other material. These may impact on the stability of the film.
Store microfilm in specialised polypropylene microfilm boxes. Cardboard, paper, and metal microfilm boxes are unacceptable for preservation reasons.
Boxes can be marked with the contents using a permanent white marking pen. Paper labels, stickers or adhesive tape of any kind are not recommended as these are liable to fall off in cold storage conditions.
Contact QSA for additional requirements if microfilm is to be transferred to QSA in the future.
Audio tapes can come in the form of compact cassettes, micro and mini cassettes (as used in old dictaphones or answering machines), open reels and even as part of motion picture films.
Video tape types range from VHS or Beta through to U-matics and in open reels.
You need access to the corresponding equipment to play audio-visual media. Many machines are very specific being proprietary and have become obsolete, unmaintained and broken or simply unavailable anywhere.
Audio-visual media should be converted to a more suitable format before the equipment or technology required to read the information becomes obsolete.
QSA can help you identify audio-visual formats and provide advice on how best to preserve them. Take photos of the media and send it to the Preservation Team.
Find more information on preserving audio-visual formats
If an optical disc becomes dusty, dirty or has fingerprints, it may be possible to clean it before it’s permanently damaged. Take great care.
- First, blow off debris with a compressed air duster. You can then wipe clean using a soft, lint-free cloth or a non-abrasive photographic lens cleaning cloth, or a very soft brush.
- Oily dirt deposits and finger marks on the data side of the disc can be removed using alcohol-based CD/DVD-cleaning fluid.
- Cleaning solutions should be applied sparingly to the disc surface and wiped off with a lint-free cloth.
- Always brush from the centre of the disc outwards to reduce the risk of scratches. A scratch across the track (from the centre) will do less damage than along them (circular motion).
- Digital Preservation Handbook, Digital Preservation Coalition
- Preserving digital records: Guidelines for organizations (1.64 MB), InterPARES Preserving Guidelines
- Digital Preservation Toolkit, Canadian Heritage Information Network
- Preserving motion picture film, National Archives of Australia
- Preserving magnetic media, National Archives of Australia
- Preserving CDs and DVDs, National Archives of Australia
- Preservation resources and archival suppliers