Re: [ARSCLIST] powder-like substance from open reel tapes

["Peter@xxxxxxxxxxxxx" <lists@xxxxxxxxxxxxx>]

John:

"Powder" on the surface of magnetic tapes has been identified in laboratory
testing as: polyester from the base film (alternately identified as
tri-mers), sodium or calcium residue from the magnetic pigment, surfactant
residue from the manufacturing process, various fatty acids from the
lubricant and flowering heads from mold.

In most instances you can tell whether it is chemical residue or mold by the
visible pattern on the tape surface PRIOR to running the tape.  Mold has a
tendency to appear as round(ish) patches or thin threads.  The chemical
residues have a tendency to collect in lines on the edges of popped strands
following a strand or group of strands around part of the curve of the tape
pack.

Mold will contaminate your machinery and can be a serious health hazard.
Non of the other chemical residues has been identified as being toxic but I
have known operators to get headaches when they became too inquisitive and
ended up with a face full of the powder.

Neither chemical decontamination nor baking work well at removing the powder
residues prior to playback and baking can actually increase the amount of
powder on the tape surface.   Tissue wiping or burnishing will usually
remove sufficient powder to allow uncompromised playback but the powder will
often re-appear after a few days or weeks.

If your tapes have been very cold, you can sometimes get long crystals of
lubricant on the tape surface.  These crystals can be re-absorbed into the
tape by gentle heating but this is a very different phenomena than the
"powder" residues.

Peter Brothers
President
SPECS BROS., LLC
(201) 440-6589
www.specsbros.com

Restoration and Disaster Recovery Service Since 1983

> -----Original Message-----
> From: Association for Recorded Sound Discussion List
> [mailto:ARSCLIST@xxxxxxx]On Behalf Of John Loy
> Sent: Tuesday, September 28, 2004 3:40 PM
> To: ARSCLIST@xxxxxxxxxxxx
> Subject: [ARSCLIST] powder-like substance from open reel tapes
>
>
> I was wondering if anyone had experienced a powderlike substance from
> open reel tapes from the early to mid 1970's. The brand of tapes are
> TDK. The powder has been gumming up the machine's transport yet has not
> impeded play or audio quality. When I go to rewind a tape however, it
> slows the machine and prevents a full rewind at which time I have to
> clean the machine. The powder is a yellowish-brown and while it is on
> the guides and heads of the machine looks organized but scrapes off
> into a power. If you have heard of or experienced this problem please
> respond and let me know what I can do about it or what effect it may
> have on my machines or the tapes in a long term storage situation.
> Please ONLY helpful, polite inquiries.
>
>
>
>   thanks,
> John A. Loy
> Audio Preservation Engineer
> Southern Folklife Collection
> UNC Chapel Hill
>