eli5 How do rewritable cds 💿 work?

Question

I know how normal cds work, they are basically aluminum molds of data in binary. So how do rewritable ones get erased and reformatted?

In: 80

Answer 1

Pressed CDs are just like that, pressed. A press puts dents into the plastic disk.

Normal writable CDs contain a material that discolors when hit with a powerful laser, so from now on it will reflect differently which the laser can detect while reading.

A rewriteable CD has a (more expensive) material that changes color based on temperature. Hitting it with a certain temperature laser makes it darker, hitting it with another temperature laser makes it lighter / transparent. That way, once a CD has been written, you can “erase” it again by burning with a different temperature.