📰 Why 'Baking' Damaged Reel-To-Reel Tapes Renders Them Playable Again

An anonymous reader quotes a report from Ars Technica: Reel-to-reel tapes are experiencing a resurgence of interest among audio buffs, but they are prone to degradation, which has been a topic of active research for many years. It's well known that applying heat can often reverse the damage sufficiently to enable playback, usually by baking the tapes in an oven. Now scientists at the US Library of Congress have determined precisely why this method seems to work, presenting their findings earlier this month on the American Chemical Society's SciMeetings online platform. The primary culprit for the degradation is known as "sticky shed syndrome," in which the binders used in a magnetic tape to hold the iron oxide casing to the plastic carrier deteriorate. They form a sticky residue that can damage both the tape and playback equipment. [...] [E]xperiments showed that when a degraded reel-to-reel tape is heated, the sticky residues melt back onto the bulk polymer layer, rendering the tape playable once again. That's why 130F is the sweet spot for baking degraded tapes; it's the melting point for the residues. "If you go any lower than that, nothing is going to happen," said project leader Andrew Davis, a polymer chemist who works in the LOC's preservation research and testing division. However, he also found that there is no single component that accounts for tape degradation, and the sticky residues don't just form on the binder layer. "This research also confirmed what we heard from audio technicians, that thermally treated tapes that were wound on reels reverted to a visibly deteriorated condition within a few weeks," said Davis. "Surprisingly, we found that when our small unwound test samples of tape were thermally treated, they appeared to be optically fine even after weeks. Clearly being wound has some effect on the tapes." That is the next stage of research, and Davis actually set up a range of samples with different treatments that he was monitoring right up until shelter-at-home policies went into effect in the Washington, DC, area. He hasn't been able to return to his lab to check on them but is hopeful that, once the lockdowns lift, there will some intriguing experimental results on that score. Beyond that, Davis hopes to extend his experiments to enclosed magnetic media, such as cassette and VHS tapes.

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