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Originally Posted by vysakh
digit is not writing cds. they are punching / pressing cds. they have some extra coating. if u look at the cd you will understand. written cds will have a colour change wheras the pressed ones dont have. due to the extra coating, they are more reliable
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Burnt/written are different from Pressed CD's. Right, but it's not about the coatings. It's about what lies beneath the coating that's different
Pressed CD's - Thin layer of acrylic is PRESSED against a glass master disc to reproduce bumps (pits). Reflective aluminium is sprayed onto this layer (on the read side) and protective clear polycarbonate plastic layer is added on the same (read side). On the back of the acrylic layer the label is applied.
Burnt (home made) CD's - The aluminium surface does not exist. Instead a reflective dye is used. The powerful laser in your CD burner will modify the reflectivity to SIMULATE bumps (pits) as in pressed CD's. This explains the colour change you observe after burning.
Did you know it's easier to damage a disc by scratching the LABEL side. Data is held in the layer just below the label. So next time you want to render a CD useless, just use a knife on the LABEL side.
Keith