Nearly 1 million analog studio tapes from the '70s and '80s, both masters
and session reels, are now in perilous condition because, as engineers
discovered to their horror nearly a decade ago, they were manufactured
with a flawed binder that absorbs moisture over time.

Problem tapes include Ampex 406 and 456 and Scotch 3M 206/207 and 250/251.
Several Agfa formulations also show the symptoms. None of those tapes are
still manufactured.