This is very true and what makes our diagnosis very difficult.
Benoit Thiebaut when he was working for PrestoSpace identified one tape
"type" (as described by manufacturer and a type number) to have at least
four different formulations as identified by FT-IR analysis (IIRC
correctly, it may have been other analyses as well).
So even within "NameBrand 123" there are significant variations.
Add to that the batch-to-batch variations, then the "running changes"
that may be subtle but still important, and we never know what we have.
With reel tapes, who knows if the reel stayed with the tape? At least in
audio and instrumentation, the assumption is: unlikely.
On the Mt. St. Helens IRIG tapes, they were using recycled tape and then
using the supply reel of the previous tape as the takeup reel of the
current tape and leaving the tapes tails out. If we assume that there
was a possibility of that happening in the previous lives of the tapes,
there was no way the reel and tape matched.
Unless we get into FT-IR analysis and have a master "key" to each
signature, I doubt we'll be able to know for certain what the tape is.
Both Benoit and Ric Bradshaw (ex IBM Tape Lab) have trounced my hopes
for a simple "pool test kit" for analyzing tapes in order to key in the
proper conservation measures.
On 2014-02-07 10:02 AM, David Crosthwait wrote:
> Thanks for this note. One then could assume that just because a
> certain brand of tape from South Korea has "predicted"
> characteristics based on prior experience that this does not
> necessarily hold true in all future situations since the shell itself
> could hold tape from a subcontractor. Perhaps this "load" of tape in
> this shell may have binder issues, therefore stickiness.
> I have experienced similar situations with 3/4" videocassettes and
> even 1" videotape where the flange and it's notations holds another
> brand/manufacturer of tape.
-- Richard L. Hess email: [log in to unmask]
Aurora, Ontario, Canada 647 479 2800
http://www.richardhess.com/tape/contact.htm Quality tape transfers --
even from hard-to-play tapes.