From: lstowell@pyrnova.pyramid.com (Lon Stowell)
Newsgroups: rec.audio,rec.video
Subject: Re: CD rot -- who gives a damn?
Date: 9 Apr 92 17:13:23 GMT
Reply-To: lstowell@pyrnova.pyramid.com (Lon Stowell)
Organization: Pyramid Technology Corp., Mountain View, CA

In article <1992Apr9.142411.20801@ux1.cso.uiuc.edu> tmkk@uiuc.edu (K. Khan) writes:
>
>I'd like to know more about this CD Rot. Since you appear to be
>knowledgeable on the subject, perhaps you could answer the following
>questions for me:
>
>1) How many rotten CDs do you have?
   
     I have about two dozen of them.  But it's the recording, not
     the CD.  >:-)

>
>2) What does CD rot look like?

    Whitish or yellowish....just like a piece of raw aluminum left
    out in the weather in a major city.

    I've scratched a couple CD's on purpose,,and you CAN see
    corrosion of the aluminum layer with a 10X-20X microscope.  The
    spread of this corrosion to adjoining tracks has been 
    disappointingly underwhelming.  And all of these test CD's
    still play even on an antique Yamaha--not noted for tolerance of
    disks.  
>
>3) What exactly *IS* CD rot? A clouding of the acrylic on the data side?
>Oxidation of the metal in the data layer itself?
>
    Several possible answers:

    A.  Corrosion of the aluminum layer.  Apparently there were
	reports that some inks and paints on the label side were
	reacting with the aluminum reflective layer.  

	Also it IS true that if you scratch the label side on most
	disks, you can penetrate to the reflective layer very
	easily..and once oxygen, sulfurous oxide, etc. plus a tad of
	H2o vapor get at aluminum, it will corrode.

    B.  A scare story generated by a certain recording company 
	hoping to justify their use of 22 K gold as the reflective
	layer.         

	Although these CD's are visually attractive, they STILL
	don't have a decent protection for the layer...just a thin
	lacquer coating, then the labelling inks.  

    C.  An April Fool's Joke put out by some wag--and attributed to
	Sony and Phillips.  

	The reincarnation of this topic every year about this time
	would tend to lend a bit of creditability to this, IMHO.

    
>4) What causes CD rot? Manufacturing defects? Poor handling/storage by the end
>user? Laser Bacteria?
>
        Sunspots.  Demons.  Yellow ink.  

	Seriously I have seen a LOT of disks with manufacturing
	defects.  Poorly burnished center holes, off-center holes,
	ragged edges, and pinholes all over the place.  I've tried
	to rot a few of these by leaving them outdoors in the LA and
	Bay area smog with underwhelming results.  

	Poor handling often scratches the label side...and the
	aluminum is immediately below that.  Dunno why the plants
	don't spend $0.01 additional and melt a thin acrylic layer
	over the aluminum as a protection.  

	If the aluminum gets exposed to the atmosphere it will
	corrode.  MOST aluminum corrosion products are extremely
	effective corrosion barriers though.  You have to
	continually expose new aluminum molecules to oxygen,
	chlorine, sulfites/ates, flourides, etc. to get the
	corrosion to spread.  The most common corrosion is the oxide
	which forms an extremely resistant barrier...sapphire just
	doesn't corrode very well as long as you don't crack it..and
	it is hard to scratch.  


>Thanks for enlightening me.

        You want enlightenment, go to Tibet...  >:-)