Inspection Techniques to Sample the Condition of Magnetic Tape
To prevent damage
during use and premature loss during storage, it is necessary to inspect
magnetic tapes on a periodic basis. Comprehensive testing of stability
and longevity is performed in government laboratories (e.g. the National
Media Lab) and professional facilities like SPECS BROS. Basic warning
signs of tape instability can often be identified using the following
This 7-Step Physical
Inspection has been adapted from a submission SPECS BROS., LLC authored
for the American National Standards Institute Subcommittee on Magnetic
Tape. To avoid serious damage to recorded materials, this simple inspection
process should be performed before putting a valuable tape on a machine
for playback. It can also be used to perform an initial evaluation of
the overall condition of older tapes in an archive.
While this examination
does not identify all problems that can occur, if your tape fails any
of these inspection criteria, it is endangered and needs attention.
Attempts to play back such tapes before treatment place them, and your
machinery, at risk.
The following inspection
procedure should be performed in the order listed. If any sign of fungus
is detected in step two, inspection should be stopped immediately:
- Check physical
container for damage that compromises the structural integrity of
the container itself. Breakage is a strong indication of improper
handling. If the container, reel or cassette is damaged, the tape
inside is also likely to have suffered damage or contamination.
- Check the
interior of the container and the edges of the tape for patterned
black, brown, or mustard colored contamination and for fuzzy or thread-like
growths that indicate the presence of fungus. Fungus can grow
on tape after it has been exposed to high humidity. Tapes with fungus
should be isolated and treated by professionals as soon as possible.
Tape with fungus can present a health hazard: if fungus is suspected
do not continue inspection!
- Smell the
tape as soon as it is removed from its container. Hydrolytic breakdown
of polyester binder creates esters that have distinctive odors but
dissipate quickly. The most common odors can be characterized as "waxy,"
"dirty socks," or "astringent/pungent" depending
on the binder. Some early tapes using an acetate base will also give
off an odor of "vinegar" if the base is beginning to decay.
Tapes with binder hydrolysis are in the process of self-destruction
and can stick in the machine during playback, causing additional damage.
Binder hydrolysis can be treated: acetate breakdown is permanent.
- With light
source above and slightly behind, tilt tape edge-on at approximately
45° away from the light source and inspect tape pack. Check
for spoking, popped strands, stepped pack, edge damage, "shiners"
and windows. These terms refer to irregularities in the way the tape
is wound onto the hub and are indications of improper handling, storage
or a badly set up machine. Spoking shows up as a pattern radiating
out from the hub and is the result of improper tension. Popped strands
and stepped pack refer to individual or groups of tape wraps that
stick up from the edge of the pack. When you shine the light on the
tape, "shiners" show up as thin strips of greater reflection
resulting from the edge of the tape being torn or folded. Windows
are gaps in the tape pack caused by the tape becoming loose on the
hub and often indicate a place where the tape has folded back over
- Check the
tape edge and the reel/cassette/cartridge for particulate contamination
and for signs of staining that may indicate liquid contamination.
Any visible contamination is an indication of poor storage or handling.
Particulate contamination can block the signal during playback and
can scratch both the tape and the playback heads. Liquid contamination
will accelerate tape decay and can often result in tape wraps sticking
- Check the
tape edge for white powder or crystalline residue and check the interior
of the container for black/brown flakes of oxide. These symptoms,
caused by a variety of conditions, indicate that the tape is beginning
to break down.
- If the tape
is reel to reel, allow a few outer wraps to hang loose and examine
for physical distortion and binder/base adhesion failure. Physical
distortion caused by improper tension will often show up on a loose
piece of tape as wavy or "scalloped" edges. Binder/base
failure is identified by sections of the tape that appear a different
color where the binder has come off. Note: If transparent or masking
tape has been used to secure the tape end, binder loss in the isolated
area under the adhesive is not an indication of binder/base
For more information,
contact SPECS BROS., LLC at: firstname.lastname@example.org
or call (973) 777 5055.
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