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CD Recording FAQ
4. CD-R media
4.7. CD-RW media
CD-RW (ReWritable) media look like cdr media, but their construction is completely different. A layer of a crystallic substance is squeezed between two layers of deelectric and heated by the laser beam while data is written. Due to its nature, a cd-rw disc has a much lower life expectancy than a cd-r one and may be written up to 1000 times, though in practice this limit is often much lower. CD-RW media are easily recognized by their grey-black colour.
CD-RW media can be written only in a cd-rw drive, since a cd-rw laser head is necessary. A cd-r drive won't even recognize cd-rw media.
Reading cd-rw media also requires a multiread capable drive. Most modern drives are able to read rewritable media, including a lot of audio cd players.
CD-RW media can be used as usual cd-r media, which means that you can write on cd-rw media whatever you would write on cd-r media, but at the speed allowed by the speed rating of the media and the drive's cd-rw mechanism. You can even overburn cd-rw media, but, if the result is a coaster, you may be unable to erase and reuse it.
During the first years of cd-rw technology, cd-rw media used to be very expensive. However, when they became affordable, cd-rw gained popularity, despite their serious disadvantages regarding reliability and performance. CD-RW media are prone to data loss and cd readers will read them not at "read speed" but at multiread speed. For example, a 32x cd reader may be able to read cd-rw media at 4x only.