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Select a Topic:
Disc Use and Handling
Cleaning Discs
Environmental
Disc Storage - Ongoing to 5 Years
Long-Term Disc Storage and Archive
Temperature and Humidity
Disc Identification for Archive
Storage Cases
Archive Storage Environments
How are Discs Tested to Determine Longevity?
How Long Will Recorded Discs for Archive Remain Useable?
Disc Use & Handling
- Handle and touch discs only at the outer edge or in the center hole.
- Do not touch the disc read-out surface.
- Do not bend or flex discs.
- Return discs to their storage case immediately after use.
- Make sure multiple discs are not inserted into single-disc tray-load readers.
- Make sure discs are properly seated in single-disc tray-load readers.
- Avoid placing discs on unclean surfaces.
- Inspect a disc’s read-out surface prior to recording or reading.
- Dropping a disc on-edge, could separate an adhesive layer and induce oxidation.
- Particularly avoid scratching or denting the label surface on a CD disc.
- Do not use pencils or ball-point pens to write on disc label surfaces.
- Do not use solvent-based markers to write on disc label surfaces.
- Use inert-based soft-tipped markers on disc label surfaces or markers specifically manufactured for disc identification.
- Never write on disc read-out surfaces.
- Do not use rectangular or odd-geometric pressure-sensitive labels on discs.
- Use only circular disc labels that are properly centered and never use labels with partial coverage.
Cleaning Discs
- Clean disc read-out surfaces with a small amount of mild dishwashing liquid diluted in clean water, followed with a straight-water wipe.
- Do not clean discs with strong solvents or corrosives – such as bleach or ammonia.
- Clean discs by wiping in a circular motion around the disc.
- Remove stubborn material with isopropyl alcohol or methanol.
- To remove stubborn dirt, fingerprints, smudges, liquid or foreign material, use a clean cotton fabric or optical lens cloth.
- When removing stubborn material, wipe in a straight line from the disc-center toward the outer-edge.
Environmental
- Do not expose discs to excess heat or high humidity.
- Likewise, avoid exposing discs to rapid changes in temperature or humidity.
- Do not expose discs to prolonged sunlight, other intense light sources or ultraviolet radiation.
- Avoid leaving discs in vehicles experiencing excessive heat and humidity.
- Discs moved within large temperature differentials, should be allowed to stabilize to ambient room temperature before use.
Disc Storage - Ongoing to 5-Years
- Discs should remain in their packaging or cases when not used.
- When possible, recordable discs should remain sealed until use. Discs stored on spindles should be twisted closed.
- Store discs in a cool, dry and dark environment.
- Store discs in clean-air environments and avoid dusty areas or where high-levels of air-borne particulates or fumes exist.
- Ideally, discs should be stored in upright, vertical positions – like a book on a shelf – inside plastic disc cases designed for optical media.
- New recordable discs should be consumed and recorded within 24 months or sooner.
Long-Term Disc Storage & Archiving
Sound practices for long-term retention of content recorded to CD-R and DVD-R discs should be used. The following are some disc archive considerations.
- When possible, use recordable discs having a gold metallic reflective layer.
- Long-term storage of critical content and data for archive should include a fundamental decision to use either CD-R or DVD-R media. Because DVD-R discs have some inherent technical advantages over CD-R discs as related to archive, it may be prudent to seriously consider DVD-R.
- Because the critical dye and reflective layers with DVD-R media are sandwiched between two polycarbonate substrates, there is less likelihood of air and moisture infiltrating and causing oxidation. Alternatively, dye and reflective layers with CD-R discs reside just beneath the top surface layer. In addition, DVD disc hardware provides improved error detection and error correction algorithms as compared to CD.
- Important content recorded to optical media for archive should always be “verified” to ensure that data itself is correct and recording was accomplished successfully. Otherwise, archived data for future retrieval may contain errors, be unreadable or perhaps not even exist.
Temperature & Humidity
According to general recommendations by the National Institute of Standards and Technology, of the U.S. Department of Commerce Technology Administration, long-term storage of CD-R and DVD-R discs should have stable temperature and relative humidity conditions:
- Temperature: ABOVE 39 degree Fahrenheit (39F), and BELOW 68 degree (68F) Fahrenheit. (Above 4 degree C, and below 20 degree C)
- Relative Humidity (RH): Twenty-percent (20%) TO fifty-percent (50%)
- For extended long-term archive, lower range temperature and RH should be considered.
Disc Identification for Archiving
- Various forms of surface labeling can be used for disc identification. For disc archive, some surface labeling options can be better than others, while some should be avoided completely. For retention of critical data and archives with optical media, avoiding any disc labeling may be prudent. Instead, consider labeling the protective case or packaging that contains the disc itself.
- If surface labeling for disc archives is necessary, DO NOT use pressure-sensitive labels. Paper-based labels can absorb and retain moisture. Alternatively, they could dry-out and deform or layers could separate. Although adhesives used with certain pressure-sensitive labels having “disc friendly” claims, may be fine for other types of disc distribution projects, to our knowledge, independent age testing has not been conducted to determine effects of long-term storage on various pressure-sensitive labeling materials and their adhesive formulations.
- Other disc surface labeling methods such as inkjet, thermal or thermal-retransfer could be suitable for long-term disc storage and archive. However, we’re not aware of independent tests conducted along these lines having published results.
- If disc surfaces used for archiving require identification, then printing or writing only in the inner disc area where data does NOT reside is the best location. Some disc printing equipment may not be able to print accurately or consistently in this confined area. If hand-written disc identification in this area is the preferred method, using soft-tip marking pens conducive to disc surfaces and void of solvents should be used.
- Because the inner-disc area offers limited space for printing or writing text, a serial number disc identification sequence can be considered. The serial number on the disc should correspond to an identical serial number on the disc’s protective case or packaging. If a table-of-contents or other information must be stored with the disc itself, it’s prudent not to include any paper material inside the disc-case. Paper can absorb and retain moisture – which could be transferred to a disc’s polycarbonate substrate.
Storage Cases
Using individual disc cases conducive to archive and long-term storage is recommended. When choosing suitable disc cases they should provide:
- Physical protection
- Prevent disc read-out surfaces from contacting the internal case.
- Buffering for rapid changes in temperature.
- Minimize or eliminate exposure to light.
- Help isolate discs from airborne contamination.
- Allow external case areas for printed, written or barcode information
Most disc cases incorporate an “internal hub”. Hubs should securely hold a disc in place within its center hole, while suspending and isolating the disc’s read-out surface from contacting any other surface area. When pressed or squeezed, hubs should release discs allowing easy removal without bending or flexing discs.
Disc cases should be plastic. Paper should not be stored inside with discs. If traditional jewel-cases are used, any paper insert should be removed. Some jewel-case designs have up to 6 trays for storage of multiple discs. For archiving, an individual case for each disc is usually employed. Doing so, eliminates retrieving multiple discs from archive when only one is needed and helps avoid the loss of discs. It can also simplify identification techniques.
Archive Storage Environments
Prolonged exposure to sunlight or other sources of damaging light can degrade CD-R and DVD-R discs. Especially when damaging light is combined with heat – which can be generated from a light source itself. Archiving optical discs in darkness is recommended. Controlling light in environments used for disc archiving is usually not an issue. Storing archived discs in opaque dark-colored cases that prevent light penetration is usually preferred. But if dark-colored cases are used to store discs in or near direct sunlight or other intense light sources, excess heat could be absorbed by the cases and transferred to discs.
If light-colored, transparent or semi-transparent cases are used for archive, cases and their discs should be stored within suitable dark, temperature and humidity controlled environments.
Disc cases used for archive should be stored upright and vertical – like a book on a shelf. Discs suspended in cases by a hub mechanism, prevent read-out surfaces to contact any other surface area. Alternatively, storing discs horizontally could cause discs to warp over extended periods of time.
How are Discs Tested to Determine Longevity?
Essentially, there are two methods to test useable data life on recorded discs:
- The first method is to record data to discs, then follow-up with periodic testing of data error-rates and readability over 25, 50 or more years.
- The second method is using accelerated life testing. The process prematurely ages disc media in laboratory settings using environmental test-chambers creating harsh stress conditions.
Tests record various forms of data to discs. Media is then subjected to elevated and reduced temperatures, varying humidity, differing wavelengths of light and surface testing. Analysis and measurement of data error-rates, readability and material breakdown, are used to project life expectancies over time.
Accelerated life testing reaches theoretical conclusions. It’s the only scientific method that can reasonably and statistically predict data longevity on discs – other than waiting decades for definitive results.
That said, many early disc manufacturers began recording data and storing discs from the 1980’s. Discs are periodically analyzed and tested for readability in an ongoing manner.
How Long will Recorded Discs used for Archive Remain Useable?
A few manufacturers offer discs specifically for archive applications and specify disc life expectancies – but most do not. Those that do, likely use costlier materials and more stringent production processes. Some disc manufacturers clarify environmental and other conditions by which discs should be stored for archive. Other manufacturers prefer not specifying data longevity because there is just no telling how discs will be stored by users. In other cases, due to production procedures, equipment utilized, as well as material and chemical formulations employed, some manufacturers of disc media find that it’s just too risky to make claims that discs will withstand the test of time.
A particular manufacturer of CD-R and DVD-R discs having a standing reputation for quality, positions some of their disc products for archive applications and states:
“We conservatively estimate that our silver CD-R will last 100 years when stored at room temperature and our gold will last in excess of 300 years”.
Another supplier of DVD-R discs recently announced a one-hundred year data-life guarantee for content recorded using their discs.
In October, 2004, the “Journal of Research of the National Institute of Standards and Technology”, published a paper that studied error rates in harsh conditions and stability comparisons of recordable optical discs. The document stated the following:
“The reliability and longevity of any storage medium is a key issue for archivists and preservationists as well as for the creators of important information. This is particularly true in the case of digital media such as DVD and CD where a sufficient number of errors may render the disc unreadable”. “Initial results show that high quality optical media have very stable characteristics and may be suitable for long-term storage applications. However, results also indicate that significant differences exist in the stability of recordable optical media from different manufacturers”.
National Institute of Standards and Technology also published an informative fifty page document titled:
"Care and Handling of CDs and DVDs
- A Guide for Librarians and Archivists"
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