Chip's CD Media Resource Center:
CD-RW (ReWritable) 1

CD-RW (ReWritable)

under construction...

CD-RW Physical Structure

The section below is from EMTEC (see Resources section).

How the CD-RW works

The need for a recordable CD was made possible by the development of a coating surface possessing two stable states, i.e., a polycrystalline state and an amorphous state. Instead of an organic dye, the reflector is covered with the above mentioned special alloy having a higher reflectivity in the "erased" condition. Heating the media/spot, with a laser beam, to the melting point of the alloy (500°C-700°C) and quenching it, converts the spot to a low reflective amorphous state (pit). Heating the same spot to the crystallization temperature (200°C) will bring it back to a high reflective or polycrystalline state. By using this technique one can also overwrite excising data.