The rewriteable compact disc is called a CD-RW. This disc allows for repeated recordings on a disc. It is relatively more expensive than the CD-R. However, in certain circumstances the benefits outweigh the cost.
While the CD-R may use a layer of organic dye, which can only be altered once, the CD-RW uses an allow that can change to and fro from a crystalline form when exposed to a particular light. The technology of this process has a special name called phase changing.
The patterns, however, are less distinct than that of other ordinary CD formats due to the greater difficulty of manipulating a metal instead of a dye.
The alloy is usually made up of silver, indium, antimony and tellurium. After heating to a particular temperature, the alloy will crystallize when cooled. Heating that particular spot to a greater temperature results in the substance becoming amorphous when cooled. By controlling the temperature, some areas have crystals and others do not. The crystals will reflect the laser effectively while the non-crystalline areas would absorb most of it.
To rewrite on a CD-RW, the alloy is first made amorphous, then reshaped using the cooler laser. The CD-RW can be rewritten as many as 1000 times.