Data on a Hard Drive is stored on platters made of either glass or aluminum. The platters are coated with a thin mirror-like coating of magnetic material which facilitates the storage of data. The data is written magnetically via the hard drive read/write head which moves along the surface of the platters without actually making contact with the platters. Unfortunately, for numerous reasons, read/write heads can "Crash" and the head loses lift and crashes onto the platter surface. In most situations, the head will briefly make contact, immediately lift back up, and the drive will go on working with no noticeable impact to the user. Sometimes a head crash damages the head. Instead of lifting back up, the heads may remain in contact with the delicate platter surface. The platter spins at a high rotational speed ranging from 5400 to 15000 revolutions per minute. This rotational velocity combined with contact from the heads is what causes rotational scoring. In extreme cases of rotational scoring, large portions of the hard drive platters are exposed as bare glass. This means that nearly all the magnetic material from a vast portion of the drive has been scratched off by the read/write head. Some minor rotational scoring can be overcome by advanced techniques to recover data elsewhere on the drive’s platters. Unfortunately, any significant scoring is very likely to remove key parts of metadata necessary to make sense of the remaining binary code. Rotational scoring also creates an uneven surface on the platter, meaning even if you replace a damaged read/write head, the new one can become damaged again by slamming into the uneven portions of the platter.