Jonathan,

I have seen this mostly on Ampex back-coated tapes and it seems to be 
some exudate from the breakdown of the tape coating(s).

What happens when you put a Q-tip with isopropyl alcohol on it? If it's 
the same stuff I saw, it seems to immediately go into solution and 
essentially disappear.

I would err on the side of caution and wear a NIOSH respirator and use a 
HEPA filtered vacuum to remove it. Also, if you are in an environment 
with others, don't do anything. Do it alone with volumes of air moving, 
again to be safe.

But, make sure it's not mold.

Cheers,

Richard


On 2022-11-07 3:01 p.m., jonathan richardson wrote:
> Wondering if any of you can help me identify a white filmy/powdery
> substance on the pack of an open reel tape. At first glance it looks like
> mold but on closer inspection it isn't. There is some kind of chemical
> breakdown happening obviously and the tape is polyester with
> back treatment. The tape is TDK GX 35/180Bm. There are other tapes in the
> same collection with the same condition but not sure of the brands as they
> are in generic boxes. The only thing in common is that they all are back
> coated.
>
> Any information on what this is and how to get rid of it will
> be appreciated.
>
-- 
Richard L. Hess                   email:[log in to unmask]
Aurora, Ontario, Canada                             647 479 2800
http://www.richardhess.com/tape/contact.htm  
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