[AV Media Matters] acetate tape and plasticizer crystals

[nathan_georgitis@hotmail.com]

Greetings from a lurker.

I recently looked at some cellulose-acetate audio tapes from the mid-1960s.
The oxide side of many of these tapes were besprinkled with spots- seemingly
crystalline, sometimes small and sometimes larger, generally clear or
whitish in color. In The Preservation of Recorded Sound Materials (ARSC,
Vol. 23.2), St. Laurent writes that the plasticizer additives in the
cellulose acetate evaporate and crystallize over time.

He doesn't describe the physical manifestation of this degradation, though.
Or say how greatly it affects tape to head contact or playback.

I'd like to know if anyone's observed anything similar and what strategies
have been employed to deal with the problem.

How does one clean magnetic tape, aside from vacuuming surface contaminants?

These tapes have been subjected to very humid conditions at times, though
the housing doesn't show any signs of water damage or biological
contamination.

Thanks in advance,
Nathan Georgitis
Graduate Student
Archives Management Program
Simmons College G.S.L.I.S.