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.

Cheers,

Richard


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.
>
>
> www.aes.org/aeshc/docs/3mtape/printthrough.pdf
>
>
>
-- 
Richard L. Hess                   email: [log in to unmask]
Aurora, Ontario, Canada                             647 479 2800
http://www.richardhess.com/tape/contact.htm
Quality tape transfers -- even from hard-to-play tapes.