@ Hapimeses
Blu-Ray discs have been tested through steel wool rubbing. To quote Verbatim:
"The Blu-ray disc recording layers consist of one metal-nitrate layer. The blue laser heats the recording layer to form a composite, which in turn forms the recording.The Blu-ray disc comes as standard with a scratch-proof protective layer, but Verbatim have gone one step further and have developed a technology that exceeds the requirements - this being the unique Hard Coat Scratch Guard coating technology.
The Verbatim Blu-ray discs, with Scratch Guard withstand finger print smudges, are less sensitive to ultraviolet light (sunlight) and are dirt and dust repellent. In addition, our Blu-ray discs have successfully passed the so called 'steel wool' test - this test involves a steel wool cloth being rubbed against the Verbatim Blu-ray disc, in effect simulating possible day to day handling."
A youtube video:
http://www.youtube.com/watch?v=o5jEbZt6AIQ