While I don't want to jump in on one side or another for or against baking versus cleaning with Pellon fabric, I was glad to have Richard mention the issue of advanced cases of Sticky Shed Syndrome. Personally, I've encountered some cases where, as the tape peeled off the reel, the oxide came completely off showing clear light through the substrate material. *Any* attempt to clean by applying a fabric to the unwinding tape would absolutely destroy the contents forever. Baking does not require any unwinding of the tape pack, thus it seems like the lesser of the evils-- and as Richard points out, the concern in many cases is a last ditch effort to save the sonic content. Microfilming brittle books and paper is acknowledging the inevitable demise of the original carrier and represents an attempt to preserve informational content regardless of whether the original is retained or thrown in the dumpster. Perhaps that's not the best analogy because microfilming wouldn't be seen as a treatment that is irreversible whereas tape baking might be. But the intrinsic value of a physical reel of tape from the 1970s is probably minimal whereas the sound on that tape may have tremendous value-- monetary, social, cultural, historical, personal, etc. I suspect that most original tapes that get baked and transferred are kept around even after the transfer has been done. True, some frequencies may have been permanently affected by either the hydrolisis or the baking, but in view of the potential for total catastrophic loss if the tape is unwound during the treatment, it seems the wiser choice-- if only for severe cases of Sticky Shed.
Thanks for the good discussion on this topic to date.