Normally we write about what’s new in media, however in this article we’re going back to our roots. Recently we’ve been asked about proper storage and care of media for archive. How long will my media last? What can go wrong? How should I store my media? The subject is pretty extensive, however we’ve scoured the internet and other references for you - We’re going to try to answer the most common questions we’re asked about media and storage.
The most common formats of media we’re asked about are Magnetic, Optical, and Film (motion picture and still) based. Each type of media has its own life expectancy (LE) and storage condition requirements. It’s best if we break down our discussion in to the different media types.
How long will my magnetic media last?
The short answer is between 10 and 30 years, however actual LE depends on a few things.
There are 3 primary factors in determining the LE of your magnetic media:
- Physical limits of the medium (the stuff data has been recorded on to)
- Environmental factors (temperature, humidity, dust, other materials in the air)
- Playback devices
Physical Limitations
According to manufacturer’s data sheets, thirty years appears to be the upper limit for magnetic media. This LE will depend on the quality of media and the specific type of media. IE. VHS tape’s life expectancy is far shorter than Digital Betacam.
Environmental Factors
Temperature and Relative Humidity (RH) are the #1 factor in determining the LE of media. Varying temperatures and humidity contribute to the deterioration of the magnetic media. The LE of VHS in typical office conditions (68-70° F at 50% RH) is approximately 12 years. By raising the humidity from 50% to 80% the LE of that same VHS tape is approximately 5 years. Again, LE will depend on the quality and type of media. VHS is more susceptible to these conditions than a Digital Betacam tape.
Playback technology
We would be fortunate if a playback technology stays current for more than 20 years. Playback equipment is getting harder and harder to find – particularly with high end formats. Like Moore’s Law stating that computing power doubles every 18 months with the cost of the technology staying the same, new playback technologies are getting introduced more rapidly as well. VHS was introduced in 1976; DVD was introduced in 1997, 20 years later. HD-DVD/BluRay was introduced this year, a short 9 years after DVD. If you are looking to store the media, don’t forget to keep something to playback the media too.
What can go wrong with magnetic media?
There are 4 primary things that can go wrong with media stored overtime or in less than ideal conditions:
1. Binder Degradation
The tape binder holds magnetic particles on the tape. If the binder looses integrity, the tape may become un-playable. “Sticky Tape” and “Tape Shed” are common terms used to describe what happens when deterioration of the binder occurs.
2. Lubricant loss
Bet you didn’t know that tape has lubricant in it did ya? Lubricants are added to the binder to reduce the friction of the magnetic topcoat layer of the tape. Lower friction will facilitate tape transport thru the player, reduce tape wear, and prevents overheating of the tape. Over time, the level of lubricant in the tape decreases. This loss is due to consumption of lubricant during playback, evaporation, and degradation.
3. Magnetic Coercivity
The coercivity of a tape refers to the tapes ability to resist demagnetization. Over time exposure of tape to magnetic fields can cause the magnetic particles in the tape to change direction causing signal loss. A magnetic tape with a lower coercivity, like VHS, will have a higher chance of signal loss when exposed to a magnetic field than say a Betacam SP or other professional tape format.
4. Substrate Deformation
The tape backing, or substrate, supports the magnetic layer of the tape. Variations in temperature and humidity cause the tape pack to undergo expansion and contraction. When the tape pack expands and contracts, it causes stress on the substrate causing it to deform. Non-Uniform winding of the tape pack can also cause deformation of the substrate.
When the tape substrate changes disproportionately, the direction of the magnetic materials on the tape move as well. The head that reads the information on the tape can not track the moved magnetic particles resulting in information loss. This will present itself as static in video, or loss of volume in audio.
How Long Does Film Last?
The short answer is 25-50 years, however, like magnetic media, it depends. When fresh acetate film is stored at a temperature of 65° F and 50% RH, the film should last approximately 50 years before the onset of acetate decay (aka Vinegar Syndrome). By decreasing the storage temperature 15°F, the film will last approximately 150 years.
Film with magnetic audio is susceptible to the same degradation as magnetic tape. Once degradation of the magnetic audio tracks on film begins, it increases the chances of acetate decay in the film itself.
Other factors that affect the LE of film are the quality of the film stock and the quality of the processing. As an example, according to
IMDB.com, 60% of the original Star Wars was shot on a film so prone to fading, the film was discontinued in the 80’s.
What can go wrong with film?
There are 7 primary things than can contribute to a films LE:
1. Mechanical Damage
Mechanical Damage is cause by mishandling of film by people or equipment. Scratches, tears, and sprocket hole damage are common types of mechanical damage.
In restoring the original Star Wars trilogy, extensive methods were used to recover the original films from mechanical damage.
2. Mold, Mildew, and Fungus
These organic contributors to film degredation are caused by film being stored in humid conditions. Typically, the organic material starts at the edge of the film and moves into the image area. The organic offenders feed off the gelatin in the emulsion.
3. Acetate Decay AKA Vinegar Syndrome
Believe it or not, plastic decays. When it decays, it releases Acetic Acid which is chemically identical to vinegar. Film will start to smell like vinegar and the film base will begin to shrink causing the film in the reel to look wavy. The film emulsion may crack or flake off.
4. Shrinkage
No, we’re not talking about
George Costanza. Along with shrinkage due to Vinegar Syndrome, films that are stored in low humidity for extended periods of time loose moisture and contract. Loss of moisture in the film base can cause the film to become brittle and crack.
5. Color Fading
Over time, the 3 dye layers (Cyan, Yellow, and Magenta) of the film begin to loose their original color. The yellow and cyan are usually the first to go giving the film a pinkish/brown color – IE mostly the magenta dye is left on the base. Films with extensive color fading look washed out and loose their contrast. The damage is permanent to the original; however there are some chemical and digital restoration techniques that may be used to resurrect another print from the original.
6. Nitrate Decay
Older 35mm films from 1893 to the early 1950’s were using a nitrate base. If you have nitrate based film you’ve got more problems than just preservation. The components used to make nitrate film are the same as some
explosives.
Once you have the explosive nature of the film under control, you have to deal with the decay of the nitrate base. The decay begins with a brownish discoloration of the emulsion with a faint noxious odor. As the decay continues, the emulsion becomes sticky, softens, then blisters and the odor of the film becomes more noxious. Finally, the film will congeal into a solid mass and turn into a brownish powder.
7. Magnetic Track Deterioration
Because magnetic media does not have near the life span of film, the combination of the two can cause problems. The iron oxide in the magnetic track may be a catalyst to early acetate decay. The magnetic coating may shed from the film base causing a loss of the audio.
How long will my optical discs last?
The quick answer between 20 and 300 years. That’s a huge range, but again, like magnetic media and film, longevity depends on a number of factors including environment and quality of media.
There are essentially 2 types of optical media, Recordable or Dye Based (CD-R, DVD-R, etc) and Replicated media. Recordable media has a LE of ~ 20 – 250 years according to the official
DVD FAQ. For replicated media, LE runs ~ 50 – 300 years.
What can go wrong with optical media?
There are 3 items that contribute to optical media’s LE:
1. Mechanical Damage
Scratches are the main culprit of problems with optical discs. Many scratches can be buffed out, however deep scratches or a high density of scratches can cause data loss. Due to their construction, CD’s are especially sensitive to scratches on the top of the disc. If a CD is scratched thru the aluminum layer on the top, the data in that section of the disc will be un-readable.
2. “Dye Rot”
Dye based recordable media should be stored in little to no light as the dye is photo sensitive and the data may be changed by prolonged exposure to light reducing the media’s LE. Inexpensive recordable discs with volitle dye layers are more susceptible to data loss than higher quality media.
3. Delamination
According to the
DVD FAQ, delamination occurs partly because some cases or players hold too tightly to the hub. Other causes of delamination may be due to storage in extreme temperatures, contaminated adhesive, chemical reactions, or oxidation of the reflective layer in the disc. Delamination may appear as concentric rings or a stain around the center hub.
How should I store my media to maximize its life?
Temperature and relative humidity are the #1 factors effecting media’s LE. Rochester Institute of Technology’s Image Permanence Institute (IPI) has come up with 4 temperature categories for storage. All temperatures require RH between 30% and 50%.
Each temperature description is an anchor point with the exception of Freezing which describes temperatures Freezing and colder.
Because many media libraries/archives are mixed media, the IPI has come up with a media storage quick reference for how best to store multiple media. Their chart accounts for less than perfect storage, giving an idea on what will be unacceptable for storage to ideal conditions.
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B&W
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Color
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Polyester
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Storage Conditions
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Nitrate & Acetate Film
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Polyester Film
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Polyester Film
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Magnetic Tape
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CD's & DVD's
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No
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Fair
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No
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No
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Fair
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COOL
54°F (12°C)
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No
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Good
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No
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Good
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Good
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COLD
40°F (4°C)
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Good
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Very Good
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Good
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Fair
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Good
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FROZEN
32°F (0°C)
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Very Good
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Very Good
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Very Good
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No
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No
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Freezing photographic materials is best as freezing slows down the chemical reactions that lead to degradation, however magnetic and disc based media should not be frozen.
Lubricant loss and separation from the base can occur on magnetic tape when frozen. With optical media, the layers that make up the disc may separate causing the disc to become unreadable. Cool or cold storage is best for archiving of magnetic or optical media.
Something to keep in mind with storage, there isn’t a 100% right way. In an ideal world, we’d freeze film and have an archive cooler for other media, however budgets and facilities dictate how we must store materials the only thing we can do is work with what we have.
For more in-depth information on the subject of storage and archival check out these links:
National Film Preservation Foundation
RIT’s Image Permanence Institute
Council on Library and Information Resources
National Film Preservation Board
