At 11:20 AM 2008-05-28, Marcos Sueiro Bal wrote:
[I think David Lennick wrote:]
And in my experience, glass based discs seem far less prone to
palmitic acid.
Interesting statement, and one I had not heard before. We just
finished surveying a few lacquer discs (almost all US), so just for
fun I tried to run a query.
Of 1,925 with metal substrate, 375 have evidence of palmitic acid
(19%). Of 123 glass-based, 22 have evidence of palmitic acid (18%).
"Further research is necessary", as they say ;-)
Hello, Marcos and David,
One of the frustrating observations to fall out of my research on
magnetic tape degradation is that there are wide variations in model
numbers and even batches of tape. I would not be surprised if the same
thing happened with discs. There are even conflicting studies--one says
that only chromium dioxide catalyzes certain types of binder
degradation while another study says that both chromium dioxide and
gamma ferric oxide catalyze a similar type of binder degradation.
From David's? original statement, one could generate a hypothesis to
test: does the aluminum substrate act as a catalyst for generating
palmitic acid in the lacquer coating? Marcos's survey numbers seem to
indicate that the likelihood of this being the case is small. There
appears to be no statistical significance between the two numbers.
Yes, more research is needed, but one might consider some confounding
factors that might explain David's perception. One that comes to mind
is: perhaps since the glass discs were known to be more fragile they
were more carefully stored.
Perhaps the best thing to think about here is to schedule preservation
reformatting (copying) for all of this fragile media while it's still
relatively easy to copy. We now have prioritization tools available in
FACET from Indiana University and your tool, Marcos, which should help
those responsible for preserving collections to determine the risk of
each collection.
The more I learn about tape degradation--and I think some of the same
may apply to lacquers as well--the more I see that analog magnetic tape
is not a good choice for extremely long-term storage. Fortunately,
obtaining high-quality disc reproduction equipment into the future
appears to be easier than obtaining equally high-quality tape
reproduction equipment.
Cheers,
Richard
Richard L. Hess email: richard@xxxxxxxxxxxxxxx
Aurora, Ontario, Canada (905) 713 6733 1-877-TAPE-FIX
Detailed contact information: http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.