Multimodal analysis reveals hydrolysis as a shared mechanism in magnetic tape degradation

Magnetic tape degradation threatens large portions of twentieth-century audiovisual heritage preserved in archives worldwide. Degraded tapes are commonly classified by their behaviour during playback, but the relationship between these macroscopic symptoms and the underlying chemical degradation processes remains unclear. Here we investigate degraded magnetic tapes using a multimodal analytical approach combining infrared spectroscopy, optical microscopy, and scanning electron microscopy. Tapes previously diagnosed with different binder degradation issues exhibit infrared signatures associated with poly(ester-urethane) binder hydrolysis that are reduced by heat treatment, but surface morphology differences govern the macroscopic behaviour of the tapes. These results show that several forms of tape degradation result from a common chemical process, while explaining differences in observed failure mode and remediation approaches. They motivate reinterpretation of tape degradation classifications in terms of underlying chemical and microscopic origins. We also demonstrate the importance of multimodal diagnostics for reliable assessment and targeted remediation of magnetic audiovisual tapes.