Date: Wed, 18 Mar 1998 01:07:21 -0800 From: Darryl Okahata <darrylo@mina.sr.hp.com> To: Greg Lehey <grog@lemis.com> Cc: hardware@FreeBSD.ORG Subject: Re: CD-R and Scanner recomendations for CD archiving of records? Message-ID: <199803180907.AA012672042@mina.sr.hp.com> In-Reply-To: Your message of "Wed, 18 Mar 1998 12:02:01 %2B1030." <19980318120201.47709@freebie.lemis.com>
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Greg Lehey <grog@lemis.com> wrote:
> On Tue, 17 March 1998 at 19:00:50 -0600, David Kelly wrote:
>
> > We've used about 400 blue Verbatim's at work so coated. You have to be
> > careful when writing on the coated side else you'll ruin the disk.
> > Apparently the layer written by the CD-R is just under the top coating.
>
> Am I missing something here? People keep talking about writing on the
> coated side. Why would anybody want to do that? Surely you write on
> the other side?
I think everyone's getting confused with the terminology. You can
write with a soft felt-tip pen on the top side of the disk -- the side
that typically has the silk-screened (?) labels. As David wrote, you
definitely do not want to use a hard-tip pen (such as a ballpoint) or a
pencil. The top-side is very thin, and the data layer is easily
damaged by pressure from any hard-tipped writing instrument.
If you want to see something "scary", take a bad disk (or a CD that
you don't mind losing), and lightly press your fingernail on the top
side (the side with the label). Now, look at the bottom side, where
your fingernail is lightly pressing from the other side. You'll see an
extremely small "dot" where your fingernail is pressing against the
disk; this is where the pressure is deforming the data layer. Move your
finger around, and you'll see the "dot" move. If you press lightly, you
probably won't damage the disk; if you press too hard, you'll do the
same kind of damage that an hard-tipped instrument will do. It's
amazing how little pressure can deform the data layer.
This is also true of the stamped, mass-produced, aluminium CDs
(such as compact audio disks). The silver CDs are just as susceptible
to damage as the write-once or rewritable CDs.
Still, for archival purposes, I'll trust a write-once CD made by a
reputable manufacturer over tape, any day. However, the only real
problem with CDRs is the low capacity (650MB). Yes, the writable DVD
drives are supposed to fix this, but I'll believe that when the
manufacturers deliver.
If people are interested in more info, see:
http://www.cd-info.com/CDIC/Technology/CD-R/FAQ.html
In particular, see these for media life info:
http://www.cd-info.com/CDIC/Technology/CD-R/FAQ07.html#[7-5]
http://www.nml.org/Publications/TechnicalReports/MediaStability/DoculabsCDRCompatability/index.html
-- Darryl Okahata
Internet: darrylo@sr.hp.com
DISCLAIMER: this message is the author's personal opinion and does not
constitute the support, opinion, or policy of Hewlett-Packard, or of the
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