Hi Karl:

I am guessing it's mold (mould to some). I would gently wipe both sides of the tape-pack with 99% or 
higher isopropynol, using a low-lint cloth (and frequently changing the surface area touching the 
tape packs), then re-shell the cassettes. My bet is that they'll then playback just fine.

If bychance they don't play well, stiction to the point of auto-shutoff for instance, bake them like 
a reel tape -- 4+ hours. I just had this work very well for me on two sticky tapes that absolutely 
would not play in any machine until they were baked, then they played just fine. I admit that two 
cassettes is not enough of a sample to draw any conclusions about baking, but it definitely worked 
in these two cases.

As for mold (mould) on tapes, I've seen that on cassettes and videotapes before. Carefully wiping 
the tape pack seems to do the trick. If you want to be extra careful, clean the heads after each 
side plays. My experience with no 1000+ cassette transfers is that they are always pretty darn 
hearty as far as magnetic media goes. If only more people recorded them with more skill, but that's 
a whole other story ...

-- Tom Fine

----- Original Message ----- 
From: "Karl Fitzke" <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, July 01, 2014 1:25 PM
Subject: [ARSCLIST] White Audio Cassette Contaminant

> Anyone care to venture any guesses on these photos and what to do about it?  For the time being, I 
> will hold my tongue and not prejudice the jury.  June 1987 recording on 3M/Scotch AVX90 cassette. 
> There's eight more where this one came from, recorded from 2nd through 3rd quarter of 1987, and 
> two Scotch AVM cassettes recorded in early 1988, with similar but significantly less on edge of 
> tape.
> -- 
> Karl Fitzke
> Audio Engineer
> Macaulay Library
> Cornell Lab of Ornithology
> 159 Sapsucker Woods Road
> Ithaca, NY 14850
> 607-254-1100
> [log in to unmask]
> Our Mission:
> To interpret and conserve the Earth's biological diversity through research, education, and 
> citizen science focused on birds.