TDK has now announced that it has successfully hit the 200GB mark in its labs. According to Reg Hardware, the company abandoned its plans to produce an eight-layer disc and instead used a new recording medium in order to achieve the 200GB capacity with just six 33GB layers. The medium is said to use bismuth peroxide, which is heated with a laser in order to form air bubbles that are then treated as bits of data. However, Reg Hardware rightfully adds that "since the density of the bubbles is clearly different from that of a standard BD - hence the higher capacity - it's unclear whether a BD-compatible drive could actually read one of these things." Of course, the 200GB discs are still at the prototype stage and presumably some time away from commercial production. 25GB recordable Blu-ray discs are already shipping, but even 50GB dual-layer ones won't appear until later this year, and 100GB quad-layer variants aren't expected until 2007.