Cd-colours

[aceizace]

I've noticed that the writable sides of cds seem to change colour quite a lot. Most cd-rs seem to be green or blue, but i have also seen some that are black. I have not seen many but dvd-rs seem to be purple. Yet - how is it that any cd you buy from a shop is always clear/white/silver (however you describe it)? I bought some really good quality cds over ebay the other day, ones that can be printed on as in professional recording, and they're still green. It doesn't bother me because i only got them because they support high speed burners, but still, it would intrest me for an explaination. Thanks.

[Phantaxus]

The blue or green colour is to do with the different photosensitive dyes used in the CDR manufacture. see http://entertainment.howstuffworks.com/cd-burner4.
htm for an explantion. I would imagine the same is true for a DVDR except that it works with a different wavelength of light so it needs a different colour. I am sure I will be corrected if this is wrong.

[Phantaxus]

http://www.tape.com/techinfo/cdr_dyes.html

[Phantaxus]

and this one for dvdr (its technical!)
http://www.tape.com/techinfo/DVD-R_white_paper.doc

[honkytonkman]

A techie-IT troubleshooter chap on a radio phone-in the other day said that the more silvery the CD's underside, the better the quality...