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RE: [AV Media Matters] Polishing of CDs


	David Seubert,quoting:
>>Optical quality polishing of recordable CDs is also very effective at
>>both transfer & subsequent playback
>Could somebody elaborate on this? I've never heard of it or read about it
>David Seubert, Curator
>Performing Arts Collections
>Davidson Library Special Collections
>University of California
>Santa Barbara, CA 93106
>805-893-5444 Fax 805-893-5749
	Firstly, I have no experience with the polishing of CDs or DVDs, its
effectiveness and benefits or the possible damage it could do to content
recorded on discs so treated. However, it is a known fact that CD and DVD
media, that are made of polycarbonate supports are easily scratched. We also
know that one side of CD media is coated with a thin layer of 'protective'
lacquer that must never be polished and be kept dry.

	It is also known that polycarbonate media are sensitive to chemicals
and solvents, and should not be exposed to water which they readily absorb
and which causes such discs to lose their flatness as they absorb water and

	I have seen one disc polishing system demonstrated at RepliTech, and
the (Japanese) manufacturer had no information whatsoever that could satisfy
my curiosity as to whether the polisher had actually been tested and
verified not to harm the content of discs. In fact the unit he demonstrated
was the prototype. So until it has proven itself by means of daring
guineapigs who have taken the risk, I remain skeptical.

	The next thing I did was to explore the marketing literature of a
purveyor of disc polishing hardware. I read in it that the 'SkipDoctor' also
referred to as 'GameDoctor' (www.skipdoctor.com) sprays the CD with filtered
water resurfacing fluid (functioning as a lubricant), followed by radial
polishing to repair any blemishes in a single or multiple pass, followed by
drying the CD with a cloth that is provided and using a felt buffing square
to restore the disc's shiny finish. 'It enables you to re-condition just
about any blemished disc in about five minutes' says the publicity. So you
take the risk of causing a disc to lose its flatness and suffer unbalance
afterward, although its scratches may disappear.

	Smart Computing (December 1999) has tested the polishing device on
two damaged audio CDs. One disc had minor scratches and surface
imperfections. The other audio CD was heavily damaged with deep scratches
that prevented them from listening to several tracks on the disc. They used
'GameDoctor'  and the minor scratches and surface imperfections vanished
from the first CD, and it played perfectly. The heavily damaged disc, on the
other hand, was not repaired completely; several songs remained unplayable,
even after a double cleaning. But they were able to listen to a few tracks
that had previously been off-limits due to disc damage, and considering the
size of the scratches on the disc, they were 'impressed that it could save
these songs. They found 'that it actually works pretty well, although it
can't perform miracles'. The do-it-yourself unit costs US $ 34.99. Learn
more about it: www.digitalinnovations.com/products/completereviews.html.

	Warning: Keep in mind that only the playback side (opposite the
label) can be polished. The label side includes the protective lacquer. Some
users have indicated that when the disc gets wet, the label ink may run
(depending on the kind of label printingink that was used), and the lacquer
may come off. Another concern I have is that the lacquer that protects the
outer and inner edges can be ground off on the edge with the polished
surface and thus open up those surfaces more quickly to oxygen and
oxidation, than would have been the case if the lacquer would have been left
intact. On the other hand, discs that are used and circulated are bound to
get scratched, and polishing may extend their life.

	Best regards,

	Ed H. Zwaneveld,
	Technological Research and Development,
	National Film Board of Canada,
	and Chair AMIA Preservation Committee
	August 9, 2000

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