Background: Sticky shed syndrome is a ubiquitous preservation challenge for recorded sound and moving images on magnetic tape. In sticky shed, degradation leads tapes to deposit a gummy residue in playback equipment, which can stop equipment during use, and can damage a sound or video signal layer. The phenomenon appears most common in analog audio and video tapes manufactured using polyester-urethane (PEU) binders beginning in the 1970s. Causes, detection, and treatment of the problem have all been subject to debate in the sound engineering and research fields. One widely applied strategy for reformatting magnetic tapes to prevent playback equipment damage and permit reformatting is to bake magnetic tapes before they are copied to a new format. The impact of baking, or of baking at differing times and temperatures, on sound fidelity in the preservation copy is unknown.
A series of extended frequency test tones were striped on fresh tape stock and then analyzed. The tapes were then baked in conditions similar to those conventionally used to reverse the effect of sticky shed syndrome and reanalyzed. This preliminary study to examine possible frequency loss produced inconclusive results. Tighter tolerances for the tape stock and record/playback equipment are required to provide the information needed.
Contributing Study:
- March 2008. Van Zelst, L., Characterization, Diagnosis, and Treatment of Sticky Shed Syndrome. Report of a study for Library of Congress Preservation Directorate.
Project Description: Initially, standardized test tones will be striped on well-characterized fresh magnetic tape stock. These will be analyzed to provide a standard for comparison with signal quality from baked tapes. Tapes will be baked according to controlled procedures and played on carefully calibrated playback equipment. The playback will be captured and the test tones will analyzed for signal frequency changes as a first-order proxy for changes in magnetic tapes baked to stabilize sticky shed.
Outcomes/Findings:
- Does baking at conventionally used temperatures and times produce signal changes on magnetic audiotapes
- Do different times and temperatures produce lesser or greater signal changes in baked magnetic audiotapes
Support: Library of Congress Library Services
Acknowledgements: Library of Congress Library Services
