Re: [ARSCLIST] CD longevity (was Re: [ARSCLIST] Reel-to-reel tapes: storage conditions and potential content retrieval)

[George Brock-Nannestad <pattac@xxxxxxxx>]

From: Patent Tactics, George Brock-Nannestad

Hello, 

Jerry Hartke wrote:

> Properly manufactured, high quality CD discs can be bent 180 degrees
> without
> cracking, while poor quality discs having lots of internal stress and high
> birefringence will easily crack and even shatter.

----- this has a lot to do with the plastic alloy used. I would not expect 
discs returned to 0 degrees after this bend to be readable, 

a) because the substrate has distorted physically

b) because there will be splitting of the protective layer and possibly the 
reflective layer. This would to a large degree depend on whether you stretch 
or compress these thinner layers on one side of the CD.
> 
> Good quality CD protective coatings, perhaps Roger's "laminations", are
> quite permanent, while poor quality discs may have pinholes in the
> coatings or metallization. 

----- a few pinholes in the metallization is not a problem, a pinhole in the 
coating is. The reason is that error correction takes care of the lack of 
data, but you need an integral and diffusion-proof coating to avoid corrosion 
spreading from the pinhole.

Kind regards,


George