From: "James Lindner" <jim@xxxxxxxxxxx> To: <ARSCLIST@xxxxxxxxxxxxxxxx> Subject: RE: arsclist Pellon and thoughts on baking/Philosophy Date: Sun, 13 May 2001 09:37:13 -0400
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A few last comments based on these and Richards follow up. I firmly think that tapes in fact DO need individual treatment - but one CAN design a system that will allow that process to be done and still process a large quantity of materials with very high quality control. That is what VidiPax is all about. I do reiterate that Pelon is ONE treatment technique that we use, there are others. I am sort of surprised that people are reacting like this is a "new" idea here. Sorry but it isn't. Pelon has been used in tape manufacture for this purpose for a LONG time. Some commercial tape cleaners Like the Elicon and the machines still made by RTI all use Pelon wiper systems. WE have used it for almost 10 years now and we have processed Hundreds of thousands of tapes (at some point you sort of stop counting - you know - billions of burgers sold at micky D's... Now exactly HOW you use the material, the way you move the tape, the contact, tension and a bunch more variables are VERY important -
So the secret is in the sauce - it took me 2 years to figure it out when I started the company!
Richards comments about RF. I was talking about audio and video - and indeed I think of RF as signal strength - which in a carrier based system is what it is - I did not want to go into too many details - but I WAS referring to audio as well. At some point I can go into the magnetics of all this. But for the moment consider a few things. There are many different aspects in tape construction that will effect the signal output as well as the signal to noise ratio. In this specific case we are going to concentrate on S/N and what impact (if any) is there in removing lose surface particulate. First consider that the particles that we are removing are not necessarily magnetized as part of the recording in the first place. Not all particles orient themselves. These "background" particles are a significant proportion of the particles on the tape. Also consider the coercivity/retentivity hysterisis curves and think that these particles may not necessarily be the ones that were oriented correctly in the first place. They are not necessarily the nicely elongated particles, nor are they necessarily the ones with high energy orientation. Consider the track width relative to these particles - their more or less random distribution along the tape (meaning that there is not necessarily more particles removed over a LOUD section of a recording as opposed to a quiet section). And so forth. Also consider the impact of a lose particle in the WRONG place - which is quite possible too - which will actually reduce signal to noise. And consider the absence of magnetized particles is no noise but silence. Stir this around in your mind - and where I think you will come out is that removing the particulate is far better then leaving it.
One final note. In the rare cases where we do bake..... yes - we do clean with Pelon after as well. While baking may make tapes less sticky - it does not deal with particulate contamination and it still is an issue even if a tape IS baked.
And finally for those magnetic geeks in the audience - the proper explanation that I did not want to get into of the above is....
C. Mee and E. Daniel, Magnetic Recording, Volume III, McGraw Hill, 1988, pp 155-170. And amazingly some of it is on the web at: http://www.ee.washington.edu/conselec/CE/kuhn/magtape/95x1.htm
which is an excellent article - specifically consider:
Noise sources[18]
Bulk-erase noise: There is a noise source due to the size and orientation of the particles in the magnetic coating. The signal to noise ratio for a band of wavenumbers from k to dk (k = 2/) is given by:
Thus, the signal to noise is proportional to the track width (w), the volume fraction of the coating occupied by particles (p such that the maximum = 1) and the orientation (F(theta) = 3/8 for random and 1 for perfect). The signal to noise ratio is inversely proportional to the mean size of the particle (s) and the standard deviation of the particle size distribution sigma. Therefore, decreasing the track size, increasing the number of particles, and decreasing the particle size; will improve the bulk signal to noise.
In our specific case we are decreasing the number the particles by a VERY small amount in porportion to the volume in the coating. Since the particle size distribution is the same in aggregate - the impact of what we do is essentially nothing from a signal to noise ratio perspective - and in actual field experience it actually seems to improve s/n because of improvement of head performance which is a VERY important factor. The gap remains clean, s/n is better - output is better for low and high energy signal strength..... you get the idea.
James Lindner
General Manager VidiPax Division VidiPax - The Magnetic Media Restoration Company
Executive Vice-President Loudeye Technologies NASDAQ Symbol:LOUD
VidiPax 450 West 31 Street New York, N.Y. 10001 212-563-1999 ext. 102 www.vidipax.com
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> -----Original Message----- > From: owner-ARSCLIST@xxxxxxxxxxxxxxxxx > [mailto:owner-ARSCLIST@xxxxxxxxxxxxxxxxx]On Behalf Of Joe Salerno > Sent: Saturday, May 12, 2001 10:10 AM > To: ARSCLIST@xxxxxxxxxxxxxxxx > Subject: Re: arsclist Pellon and thoughts on baking/Philosophy > > > Considering the limitations of either pellon or baking tapes. I agree that > the migration must take place but I would not abandon the > original artifacts > until they become completely unusable. Assume that in the near > future pellon > was proven conclusively to be superior (minimal or no damage to originals > and successful retrieval) to tape baking by some small margin. If it is as > time and labor intensive process as it seems, would not baking "win" the > contest on virtue of limited archival funding? Tapes can be "batch baked" > (I've invented a new term) whereas the pellon process would seem > to require > individual attention to each roll. > > Joe Salerno > Video Works! Is it working for you? > PO Box 273405 - Houston TX 77277-3405 > http://joe.salerno.com > joe@xxxxxxxxxxx > Fax: 603-415-7616