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Subject: Glass audio discs

Glass audio discs

From: Clara Deck <clarad<-a>
Date: Friday, December 19, 2008
Linda Kent <linda.kent [at] dcr__nh__gov> writes

>I am processing and cataloging several glass-based audio discs of
>interviews from the 1930's and 1940's. The records have recording
>material only on one side--the non-recorded side is glass. The
>records are large--about 14 inches in diameter and are very
>fragile--two are already broken.
>Any thoughts or experience in working with these records? I am
>unable to play them so cataloging will be a challenge but I am most
>concerned that they receive the processing and preservation they
>need to avoid further breakage, at least until we can find a way to
>copy them onto more current media.

Glass audio discs are test pressings or ephemeral recordings (i.e.
from live radio broadcasts).  The disc is made by flow-coating an
aluminum or glass disc with a sheet of cellulose acetate. The Zenith
Company, among others, provided prepared blanks to the recording
industry.  The discs received data from live performances using
specialized recording equipment that cut grooves in the hard polymer
coating; hence the term "cut a record".

Some of the acetate discs in our collection have condition problems
including delamination, cracking and mold.

The acetate coating is very susceptible to damage from excessive or
cycling temperature. All the problems associated with cellulose
acetate degradation plus the issue of poor adhesion make these
abject quite fragile.

We are in the process of inventorying, surveying and copying some of
our acetate discs that are in good enough condition. We use a
special turntable, an "Esoteric" brand transcription turntable.  It
has a long enough arm and sufficient clearance to be able to play a
16 inch diameter record.

Clara Deck
The Henry Ford
20900 Oakwood Blvd.
Dearborn MI 48121
313-982-6100 ext 2566

                  Conservation DistList Instance 22:37
                 Distributed: Friday, December 19, 2008
                       Message Id: cdl-22-37-007
Received on Friday, 19 December, 2008

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