CD-RWs (Compact Disc-ReWritable) enable the repeated writing of data onto a disc by using special alloys possessing what are known as "phase-change" properties. After being heated to a liquid form, certain alloys retain an amorphous condition on sudden cooling, instead of recrystallizing. When heated by the writing laser beam of a CD-RW writer, the alloy is transformed from a crystalline state to this amorphous condition. When the writing laser beam burns data on a CD-RW, it accordingly creates a stream of amorphous, low-reflective spots (recorded state) interrupted by crystalline, high-reflective spots (erased state), these two states representing the 0s and 1s of digital data, which can then be read by a reading laser beam. Data is erased on CD-RWs by using an erasing laser beam, which is too weak to melt the material, but heats it to crystallization point, and then allows the material to cool slowly, restoring the alloy to its crystalline state, and effectively erasing the 0s. The use of phase-change alloys enables a CD-RW to be rewritten over 1,000 times.