This is a fairly useless piece of trivia, but it saved a recent movie rental experience for me so I figured I’d share it.
I typically wash scratched or otherwise unreadable DVDs or CDs in warm, soapy water and then dry them with a soft, non-abrasive cloth. Discs which are not readable after this washing can be repaired in another manner. Scratched — even significantly scratched — DVDs and CDs can be “repaired” by rubbing conditioner into the surface of the data-side of the disc. I met success in this endeavor by pouring conditioner liberally onto the surface of the DVD — I used a blob roughly the size of a quarter — and then rubbing it all over the surface until most of it disappeared. There was some residual conditioner left on the disc so I wiped it off with a tissue, being careful to not leave tissue particles behind.
The DVD was really in bad shape when I got it — the movie hardly played at all — but I managed to play through the entire movie with only a few skips after the conditioner-fix.
I’m certainly open to hearing other methods of fixing scratches on optical discs!