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Analog tape is inherently noisy. With state of the
art software and hardware Creative Forensic Services
can help restore the recorded signal to the best
audible condition. Many types of recordings are
candidates for audio restoration. Recorded Evidence,
Music, Interviews are just a few categories that
qualify for restoration. Archiving these old
recordings can be essential to preserving the past.
Time is the enemy. Make no mistake these recordings
will not last forever. It could be a matter of time
before the signal to noise ratio and deterioration of
the oxide renders them unrecoverable. In some
instances the tape is not even playable without being
baked in a dehydration oven.
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The first magnetic tapes were manufactured by BASF in
Germany in 1932. These were designed with iron
carbonyl as the magnetic pigment mixed into the
cellulose acetate carrier. Production soon moved to
iron oxide coated onto cellulose acetate rolls cut
into uniform strips wound onto plastic or metal hubs.
Recordists began recording sound on magnetic media in
the twenties in the form of magnetic wire. After
World War II, the advantages of tape in terms of
sturdiness and the ability to edit by cutting and
splicing made tape preferable to wire as the magnetic
medium of choice. Tape consists of a coating of a
magnetic pigment, typically iron oxide (Fe2O3), on a
long strip of polyester (polyethelyne terephthalate)
base film. This base film has been used since the
mid-sixties as a replacement for acetate bases film
that was prone to chemical instability. Chemical
instability reared its head again in the
mid-seventies when two significant tape manufacturers
changed their dispersion formulations by introducing
a polyurethane binder that, in time, turned
hydroscopic and broke down as it absorbed water
molecules into the long hydro-carbon molecular
chains. The tape coatings became sticky and shed
oxide onto all tape recorder parts in their path,
including heads, guides, rollers, and capstans. This
is commonly called sticky-shed syndrome. Although the
problem was confined to two of the four major tape
manufacturers (neither BASF nor 3M studio tapes
suffer from the problem because neither manufacturer
used the hydroscopic binder), all magnetic tapes have
been tainted by the defect. Information can be
recovered from the "stick-shed" tapes by heating them
at a very low temperature in order drive the water
out of the binders.[1] The baking method is a
one-time solution to the problem because the binder
remains unstable. Tapes that do not show the
breakdown syndrome do not need any special treatment.
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