RE: [AV Media Matters] Video storage

[Jim Wheeler <Jimwheeler@aol.com>]

Jerry

By "imprinting", I assume that you are referring to what I call
"print-through".

Briefly, print-through is the result of a strong magnetic signal on one
layer
of tape magnetizing non-aligned magnetic particles on an adjacent layer of
tape.  These non-aligned magnetic particles are called "thermal idiots" and
are free to switch north-south when they are near a large magnetic field.

Print-through is most noticable at long wavelengths which occur mainly on
reel-to-reel analog audio tapes.  Print-through is non-existant at the short
wavelengths of video.

Print-through starts the instant two tape layers come in contact.  Most of
the thermal idiots line up in the first few minutes/hours after the two
layers come together.  After a few days/weeks, the process is essentially
complete.  So, rewinding a tape after a few years will not effect the
print-through.

That's not totally true because you can decrease print-through by running
the
tape on a tape machine two or three times.  The thermal idiots return to
their random state because of the mechanical stresses that occur when the
tape runs past a tape guide.

Jim Wheeler