More than 40 million magnetic tapes of various types are held in cultural heritage institutions within the United States. A majority of magnetic tapes were produced using polyester urethane (PEU) binders, which are known to degrade via hydrolysis. Degraded tapes are currently identified through visual inspection followed by playing. However, if degraded tapes are played, they are likely to stick and shed onto player guides and heads, resulting in irreversible data-loss. We have previously evaluated attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) in combination with principal component analysis (PCA) and linear discriminant analysis (LDA) as a relatively accurate, rapid, and non-destructive approach for identification of naturally-degraded magnetic tape. The complexity of magnetic tape analysis is derived from the variation of tape formulations produced over 30 years. Additional to the many different formats, name brands, and models of tape, formulation optimizations within the same batch number have been reported. Observations of infrared spectral changes between tapes are difficult to assign, since spectral changes could be due to formulation differences, degradation status differences, or both. Spectral changes due to degradation status can be more easily identified if variations due to formulation are not present. This can only be done through the artificial aging and spectral analysis of one tape at a time. However, many are skeptical of artificial aging and its ability to represent natural degradation. We have artificially aged tapes in environments of increased temperature and humidity. Artificially-aged tape spectra were compared to naturally-aged tape spectra using PCA and LDA. This was done by projecting spectra of artificially-aged tape spectra onto a PCA plot of naturally-aged tape spectra. LDA was used to determine classification abilities of both naturally-aged and artificially-aged spectral data sets. The results from this experiment demonstrate the differences and similarities seen between and within naturally-aged tape spectra and artificially-aged tape spectra. Ultimately, the ability of artificially-aged tape to represent the phenomenon of degradation in naturally-aged tape using ATR-FTIR and multivariate statistics is better understood.

Comparrison of naturally-aged vs. artificially-aged magnetic tape degradation using infrared spectroscopy and multivariate statistics

248th National Meeting (2014)

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