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

The data layer is made of a metal alloy that has multiple solid states. When exposed to a very high temperature, it melts and resolidifies into a less reflective form. When exposed to a lower (but still high) temperature, it shifts into a crystalline form that’s more reflective. The two forms function similarly to pits and lands, though it’s different enough that a reader needs to be designed to support it.