Right, for laser to use reflection you need to have dark and lioght, and the chemical dye layer provides a lot of that. bumps in media cause thinner dye above bump, though DVDs can use micro-bumps or micro depressions similarly.

One thing, 3M makes black watch media, and TDK and PNy have soemthing similar. These are all one-time disks but are heavy carbon for heat resistance. I would use them for critical data only, they are 4-5 times the cost each of normal CDs,but CD-RWs that are good can use them and later read from them.

They use a heavy carbon content layer instead of more heat-volatile dye, and burners have to use a hyper hot burn to record as the media has to be flowing hot to get the havy carbon displaced enough by bumps to casue a difference in reflection enough to read later. They are used for longer term archive storage. Plextors can do this, many DVD burners can do this if very good software is used. Essentially, this is what is used for mastering also, metallic base plus carbon content in substrate for heat stability and to protect the (thicker than on most CDs) foil from melting and flowing flat again.

John.