I remember as a child that one could "knock the magnetism" out of a weak
magnet by hitting it with a hammer, or subjecting it to some form of
shock. I wonder if the fast vibration of the tape under high-speed wind
could also be a contributing factor.
On Fri, Mar 13, 2015 at 9:37 AM, Richard L. Hess <[log in to unmask]>
> Thanks, Goran, I missed that when looking at the same site yesterday!
> I do not have a complete understanding of print-through, but there is
> something I think I know: While an ideal tape would be made with magnetic
> particles that had the same ability to hold their field, in reality, there
> is a statistical distribution (I'm specifically not saying "Gaussian") of
> magnetic particles in tape. The problem particles are the ones that are
> easily magnetized.
> Some will always be flipping magnetization (sometimes referred to as
> "thermal idiots") and that number increases with temperature. Also, as
> noted elsewhere, external bias contributes to the print through phenomenon.
> The 0.5 G magnetic field of the Earth contributes to it.
> So yes, the thermal idiots and their close cousins will forget once they
> are removed from the magnetic influence that caused them to all march in
> line in the first place.
> There was a brief mention of tape lifters reducing print-through when the
> tape is wound over them. If they are magnetized, that would be equivalent
> to skimming. Skimming is mentioned in the Echoraser AES paper [Radocy,
> Frank. 1959. "A New Device for the Reduction of Print-Through" Vol 7, No 3.
> July. p129-132. E-lib ID 6258]. However, there is the possibility that
> magnetostriction may also be a factor. Sharp bending radii (sharp as in
> relation to recorded wavelength) may cause partial erasure in some recorded
> media. Unfortunately, this effect was never fully explored to the best of
> my knowledge.
> The Bertram paper I mentioned yesterday is Bertram, H. Neal, Michael K.
> Stafford, and David R. Mills. 1980. "The Print-Through Phenomenon" Vol 28,
> No 10. October. p690-705. E-Lib ID 7738. In glancing through it is well
> worth obtaining, but will require in-depth study.
> On 2015-03-13 9:28 AM, [log in to unmask] wrote:
>> That is the part I don't understand.
>>> Why would it propagate outwards
>>> more easily than inwards? It's the
>>> same distance either way.
> Richard L. Hess email: [log in to unmask]
> Aurora, Ontario, Canada 647 479 2800
> Quality tape transfers -- even from hard-to-play tapes.
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