Be glad you don't have to deal with this kind of thing:
http://everist.org/pics/misc/20200719_6831_wet_tapes.jpg
A bunch of PDP 8 system tapes. That were literally soaking in liquid water when
recovered.
Yes, that is mildew. They are nearly dried out now.
Still to be determined if they can be manually teased apart intact enough to be read.
After deciphering what they all are, from remnants of the labels and a paper list that
was with them.
Hopefully these are already online somewhere. If not, then a lot of work to recover.
The DEC mag tapes... sigh. Still not even thinking about them. Just slow drying.
Guy