This repair rate includes discs with solvent damage and those that are heavily gouged. Check both sides of the disc for any cracks. Cracks sometimes look like a scratch, but cannot be repaired. Hold the disc up to a bright light, with the PLAY surface facing you. If any patches of light show through, then the data has been damaged and cannot be repaired.
Most CDs are repairable, and some minor data loss can be tracked over without problems.
Following these guidelines will help you get the best possible results from your repaired disc. There is no process that can restore damaged or missing encoding from the label side, therefore it is important to screen your discs carefully before sending them in for repair. Damaged or missing encoding cannot be repaired or replaced. Most players are able to track over minor damage without much difficulty, especially scratches through the data that radiate from the center outwards. Scratches to the data that follow the direction of play will usually cause a problem.