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Re: [ARSCLIST] Retro Vinyl CDs
From: Patent Tactics, George Brock-Nannestad
Mike Richter wrote
> The Verbatim discs are necessarily compliant with the CD standard and
> therefore no more than 12 cm in diameter. A disc of the dimensions of
> a "45" (half again as wide) could not be inserted into, or read or
> written by a Compact Disc device.
----- precisely my point!! Is it a "reduced" "45" we see, or the centre of
a "full-size" one??
> Both sides of some blanks are clear. My guess is that George refers to
> the upper surface with an acrylic lacquer over the metallizing rather
> than the lower which is polycarbonate.
----- I am referring to and cutting a record into the thick polycarbonate
layer that is the body of the CD.
In that case, extreme caution
> is needed for any incision: the layer is thin and fragile and any
> damage to the metal layer is fatal to the (optical) recording. An
> overcoating will reduce the risk, of course.
----- As my 78 rpm cut is at least 100 microns deep, no amount of
overcoating would reduce the risk, if I were to cut the lacquer side.
However, my cuts are circumferential, and hence even cutting the
thick polycarbonate makes the disc unreadable where my cut is. As
the digital recording starts inside and goes out, and my 78 rpm cut
starts on the outside, I only have to stop cutting before I reach "end of
file" markers on the 90 second CD recording. I will have to check with
a chemist to find out if it would create a health risk to cut through the
lacquer layer and liberate what will be phtalocyanine in power form
that might be breathed by the "recording expert" (ME, in other words).
P.S. I own one VideoDisc all told, and I do not want to waste that on
experimenting with cutting 78 rpm grooves in it. It would give me two
good sides, however, and at 12 inches at that.
> At 12:04 PM 5/4/2003 +0200, George Brock-Nannestad wrote:
> >----- I can see confusion indeed, because I do not know any
> >mechanical recordings actually pressed in polycarbonate. However,
> >pressing in polycarbonate is a part of the ordinary Audio CD
> >manufacture (and actually the wobble track in CD-R is pressed too).
> >Incidentally, as a gimmick, I have cut 78 rpm grooves in the outer
> >parts of the clear side of a CD-R, giving me a maximum of 90 seconds
> >of sound, while the CD-R contains the same selection as an only track
> >in a digital form. Using 33 1/3 rpm and 400 grooves to the inch would
> >give quite a self-contained archival medium: when the digital part of
> >the CD-R breaks down after the 361 (or whatever) years, we still have
> >the mechanical version to play.