- Media preservation
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Preservation of document, pictures, recordings, digital content, etc., is a major aspect of archival science. It is also an important consideration for people who are creating time capsules, family history, historical documents, scrapbooks and family trees. Common storage media are not permanent, and there are few reliable methods of preserving documents and pictures for the future.
Contents
Paper/prints (photos)
Color negatives and ordinary color prints may fade away to nothing in a relatively short period if not stored and handled properly. This happens even if the negatives and prints are kept in the dark, because the ambient light is not the determining factor, but heat and humidity are. Because color processing results in a less stable image than traditional black-and-white processing, black-and-white pictures from the 1920s are more likely to survive into the long-term future than color films and photographs from after the middle 20th century. The color degradation is the result of the dyes used in the color processes.
Color prints made on most inkjet printers look very good at first but they have a very short lifespan, measured in months rather than in years. Even prints from commercial photo labs will start to fade in a matter of years if not processed properly and stored in cool, dry environments.
Black-and-white photographic films using silver halide emulsions are the only film types that have proven to last for archival storage. The determining factors for longevity include the film base type, proper processing (develop, stop, fix and wash) and proper storage. Early films were coated onto a nitrate base material which was prone to combustion if stored in uncontrolled temperatures. Nitrate film was replaced with acetate-base films. These Cellulose acetate films were later discovered to outgass acids (also referred to as vinegar syndrome). Acetate films were replaced in the early 1980s by polyester film base materials which have been determined to be more stable than nitrate- and acetate-base films.
Documents/Books
With documents for which the media are not so critical as what the documents contain, the information in documents can be copied by using photocopiers and image scanners. Books and manuscripts can also have their information saved without destruction by using a book scanner.
Where the media need to be preserved, for example if a document is a sketch of crayon by a famous artist on media (say paper) a complex process of preservation may be used, depending on the condition and importance of the item including gluing the media onto more stable media. Other considerations in preserving paper/books may include
- damaging light particularly UV light, which fades and destroys media over time by breaking down the molecules.
- atmosphere contains small traces of sulfur dioxide and nitric acid which turn media yellow and break the fibers down.
- humidity and moisture also aid in the breakdown of media. Too much used, the document is attacked by bacteria and too little used, cellulose material breaks down.
- Temperature, particularly elevated ones, can destroy some media. Low temperatures can cause the water to form crystals which expands destroying the fiber structure of paper based documents.
Online Photo Albums
There are now a number of websites that will allow you to upload photos and videos. Sites such as Snap Fish,Fotki, and Flickr are helping people store digital versions online. However, digital preservation for the long-term is still an issue.
Most sites require you to scan the images yourself to your own hard drive and then upload them via their website. The disadvantage to this is that not everyone has the knowledge or the ability to scan images themselves. If you cannot scan the image yourself then you need to arrange for someone else to do it for you.
The alternative is to send all those old photographic prints, slides, negatives and videos off to be digitized and then returned to you. Some sites will return the prints, slides and negatives with a CD on which the digitized images appear.
Most sites will require you to either pay a membership fee or make a purchase of one of the items they sell on their website within a set period of time or your account will be deleted along with your images. So when choosing a photostorage service ensure you read the "fine print" to find out what their conditions are. For images you wish to preserve for generations, storing them in multiple formats may be appropriate, as digital preservation is not assured by merely posting photos on a photo site.
Magnetic media, video cassettes, tapes, hard drives
As with CDs and computer hard drives, Magnetic media such as audio and videotapes have a very limited life span.
According to digital storage experts, media such as zip disks, CDs, or DVDs last only a definite period before they begin to degrade,[1] although the fact that these media formats are recent inventions combined with a high rate of change and improvements in these technologies makes it difficult to determine how long digital media will last. Manufacturers claim minimum lifetimes of 50 years for CD-Rs and 25 years for CD-RWs. These experts suggest that digital images be transferred as new media are developed to ensure that they are preserved.
Audio and video tapes require specific care and handling to ensure that the recorded information will be preserved. For information that must be preserved indefinitely, periodic transcription from old media to new ones is necessary, not only because the media are unstable but also because the recording technology may become obsolete.
The magnitude of the problem of magnetic tape deterioration is just starting to be realized. According to some research, there is a good chance that magnetic tape older than 10 years will deteriorate[citation needed]. The threat comes from several sources, but the largest threat is chemical in nature, coming from the breakdown of the binder, or glue, that holds the magnetic particles to the polyester base of the tape. As this occurs, the tape often gets coated with a tenacious adhesive that makes it extremely difficult to play.Tape which has been stored in hot, humid conditions is particularly vulnerable to this phenomenon. In some cases the problem can be so severe that the magnetic material literally falls off or sheds from the base, leaving a pile of dust and clear backing. Before the problem becomes so advanced, archivists can bake the tape and make a new copy. Alternately, a digitally encoded copy of the tape can be made, so that its content can be preserved indefinitely as a digital data file.
This problem has been known for some time, but the extent of both the problem and the catastrophic effect it has on magnetic media is just now[when?] gaining visibility. It is also common[citation needed] for computer floppy disks to degrade over time, as the lubricants inside the plastic jackets of many older floppies promote the decay of the magnetic medium. Also, the alignment of the magnetic particles of the disk substrate may gradually degrade, leading to a loss of formatting and data. Early laserdisk media were prone to degradation as the layers of the disk substrate were bonded with an adhesive that was vulnerable to decay and would crumble over time. This would lead the different layers of the disk to peel apart, damaging the pitted data surface and rendering the disk unreadable.
Media at risk include recorded media such as master audio recordings of symphonies and videotape recordings of the news gathered over the last 40 years. Threats to media that must be considered when archiving important record media include accidental erasure, physical loss due to disasters such as fires and floods, and media degradation.
Along with the actual media being degraded over the years, the machines that are available to play back or reproduce the audio sources are becoming archaic themselves. Manufacturers and their support (parts, technical updates) for their machines have disappeared throughout the years. Even if the medium is vaulted and archived correctly, the mechanical properties of the machines have deteriorated to the point that they could do more harm than good to the tape or disc being played.
Many major film studios are now backing up their libraries by converting them to electronic media files, such as .AIFF or .WAV-based files via digital audio workstations. That way, even if the digital platform manufacturer goes out of business or no longer supports their product, the files can still be played on any common computer.
There is a detailed process that must take place previous to the final archival product now that a digital solution is in place. Sample rates and their conversion and reference speed are both critical in this process.
See also
References
- ^ Optical Storage Technology Association, "Technology Q&A, Understanding CD-R & CD-RW, Disc Longevity," http://www.osta.org/technology/cdqa13.htm
External links
Wikimedia Foundation. 2010.
