I was hoping that someone can tell me if the following statement is true or incorrect:

A colleague was telling me that you can tell the difference between an audiotape that was recorded on an acetate tape, versus one that was created on a polyester base, by holding the tape up to a light source. The colleague went on to say that light will pass thru the acetate tape, whereas it will not pass thru polyester tape.  

I found this rather strange because with film, the opposite is true, light will not pass thru an acetate film, but will be able to shine thru the polyester film. 

I personally believe that what the colleague was seeing had more to do with the fact, that since acetate tapes are much older, that the audio packs are going to be looser, and that what she was actually seeing is the light coming thru the gaps. 

Any thoughts on this would be greatly appreciated.

Thank you,
Lance Watsky
Preservation & Media Specialist
The Georgia Archives
5800 Jonesboro Road
Morrow, GA 30260
678-364-3764 (phone)
678-364-3860 (fax)
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www.GeorgiaArchives.org