Sticky Shed Syndrome in Magnetic Tapes: Characterization, Diagnosis, and Treatment
Background: The Library of Congress Conservation and Preservation Research and Testing Divisions are conducting research to resolve uncertainties about sticky shed syndrome (also called “sticktion”), 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. Unanswered questions concern causes, detection, and treatment of the problem.
Contributing Study: Van Zelst, L., “Sticky Shed Syndrome: Characterization, Diagnosis, and Treatment
Project Description: The purpose of this study was to understand the phenomenon of sticky shed, to identify a diagnosis tool, and to resolve important treatment questions. The study used a variety of sophisticated analytical and experimental methods to examine three types of Ampex tape widely regarded as susceptible to sticky shed.
Outcomes/Findings: The study resulted in the following key findings:
- Sticky shed results from the degradation of the binder that holds the magnetic particles to the base tape.
- While
storage at lower temperatures should increase tape lifespan, and lower
humidity will decrease the rate of degradation that produces sticktion,
PEU binders appear inherently instable. Magnetic tape made with such
binders must be assumed to have a finite lifespan.
- Several remedial techniques enable playback of “sticky” tapes,
but none stabilizes the material. Storage conditions may impact recurrence
speed, but sticky tape damage is irreversible and reformatting should
be given high priority. This does not negate arguments in favor of retaining
damaged masters in stringently controlled low temperature and humidity
storage, in anticipation of future improved reformatting options.
- Among common remedial treatments, baking and dry cleaning
have advantages and disadvantages.
- Attenuated reflection Fourier transform infrared spectroscopy (ATR-FTIR) may meet the pressing need in audiovisual archives for a relatively fast, simple, and non-destructive diagnostic to identify sticky shed syndrome before playback. Further research is needed to demonstrate the utility of the method of a sampling of sticky tape from in a wide range of manufacturers and formulations.
Support:
Library of Congress Library Services
Acknowledgements: Library of Congress and the staff of the Preservation Directorate
Updates:
March 2008. Van Zelst, L., draft final report submitted March 2008. Characterization, Diagnosis, and Treatment of Sticky Shed Syndrome. Report of a study for Library of Congress Preservation Directorate.