Over the years I bought lots of compact-discs. The collection is massive (several hundred discs) and some of the discs are more than 20 years old, and to my mind in perfect condition. In order to preserve this wonderful collection for the future generation I decided to create perfect copies as FLAC files using EAC. Easy task: Install EAC, put disc into drive, click a button and wait. But there’s a catch. Due to the age of some of the discs some of them cannot be read properly. I checked the surface and it looks pretty perfect. No scratches, no marks, nothing. But the drive still had serious issues reading the disc. I use a new Asus BW-16D1HT and a new Asus DRW-24D5MT to extract the audio data. Very good drives by the way.
Still, EAC told me about read and sync errors on some discs. So, I canceled the extraction and again looked at the surface of the disc. Now, there were thin, matt clouds of some kind of patina on the discs, which were previously not visible. I guess, the laser made them somehow visible.
Since I was unable to remove them with a cloth and I didn’t want to ruin the disc, I tried a wet glasses cloth, and to my surprise it worked. Put the disc back into the drive and it had no issues reading it.
The downside of this is, since the patina is not visible prior trying to read the disc, I have to clean every disc before I put it in the drive regardless of if it’s dirty or not.