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Submitted by pjm on 23 October 2002 at 13:01

Our archives have been handed over a number of reel tapes containing statistical data. The tapes must have been stored under unfavourable conditions, since they seem to be stuck together. We do have the equipment to read and copy them, but don’t want to incur the risk of playing them, since this may destruct them. Is there anything we can do?

Answered by swissed on 23 October 2002 at 14:17

Scope
Your question is about preservation ex post, also called “Digital Archaeology”.

Answer
The case you’re confronted with is a common example of what can happen if the necessary preservation precautions are not made early enough. However, there are some possible ways to recover data from damaged support media. But first of all, and before undertaking any recovery effort, there are a number of questions you need to address to determine whether the recovery is worth it, or, so to speak, to analyse the cost-benefit ratio. Data recovery is often possible, but always a delicate and costly task. Therefore you need to answer the following questions:
- What kind of data is stored on the reels?
- Are these data available anywhere else, or can they be generated anew?
- Are they valuable enough to warrant recovery?
- What format are the data stored in? Is it obsolete, or will you be able to easily access the data once they are recovered?

In the case of valuable data in a known format that are not available elsewhere, recovery may be a viable solution and worth the costs.

Magnetic media, such as tapes, are subject to a variety of risks, since all their constituents can deteriorate. The magnetic particles that hold the information can corrode or oxidise. The binder, composed of polymer chains and containing the magnetic particles, can absorb water; thus the polymer chains are broken up and the tape becomes sticky (as happened probably in your case). The substrate supporting the magnetic layer is more stable, but may change dimensionally, thus causing mistracking. The tape’s lubrication can get lost over time, not only causing a loss of tape flexibility, but also contaminating the player or other tapes. Improper storage accounts for most of these problems, such as climatic conditions or tapes wound too loosely or unevenly.
Measures suggested and used for recovery include amongst others:
- Controlled heating can reverse the sticky shed syndrome, although not permanently.
- Mistracking can be corrected by re-spooling the tape.
- Re-lubrication can make up for lubricant loss.

There exist several data recovery firms and organisations (some listed in ROSS/GOW [1999] below). Offers you can expect include a diagnosis to establish whether recovery is viable (for a fee of a few hundred Euros), facilities for different support media, custom-built software utilities for recognising data types, and so on. Recovery costs for portions of a few gigabytes of data from tape (or hard disk or others) typically range from one to several thousand Euros.

As there are numerous risks involved, we recommend you proceed cautiously and to ask for additional advice. Any unsuitable handling can completely destroy the tapes. You may benefit from contacting other organisations facing similar problems, your National Archives, the Association of Moving Images Archivists (www.amianet.org), the archives of the arsclist listserv (available at www.arsc-audio.org/arsclist.html), and others.

References
ROSS, Seamus; GOW, Ann: Digital Archaeology: Rescuing Neglected and Damaged Data Resources. A JISC/NPO Study within the Electronic Libraries (eLib) Programme on the Preservation of Electronic Materials. JISC 1999. ISBN 1 900508 51 6. http://www.ukoln.ac.uk/services/elib/papers/supporting/pdf/p2con.pdf


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